Chapter 10

 

         WESTERN RESEARCH ON INSECTS AS FOOD AND ANIMAL FEEDSTUFFS

 

                                                                    Introduction

 

            It is well-known that insects are an attractive and important natural source of food for many kinds of vertebrate animals, including birds, lizards, snakes, amphibians (toads, frogs, salamanders), fish, Insectivora and other mammals (McHargue 1917; Frost 1942, pp. 62-63; Brues 1946, pp. 399-407, 418; and many others).  McHargue cites a U.S. Biological Survey investigation of the stomach contents of 14 species of wild birds revealing that approximately 50% of the annual food consumption consisted of insects.  McHargue notes that since insects are available for only about half the year, the wild bird diet consists almost entirely of insects during the seasons when they are present.  McHargue states (p. 634): "The avidity with which domestic fowls, when allowed to range, seek insect food is familiar to all, and it is a well-known fact that poultry thrive best when they have access to this kind of food."

            Thus, while looked upon in the West with disfavor as food for humans, insects have attracted occasional research attention as feeds for domesticated animals, particularly poultry, swine, freshwater fish, and certain zoo, laboratory and household animals.  The vast majority of studies in the West have dealt with the nutritional value of muscoid Diptera larvae/pupae used to recycle nutrients from poultry manure or other organic wastes as a high-protein source for broiler production.

            Redford and Dorea (1984) determined the water, ash, total nitrogen and fat content for the worker and soldier castes of nine species of Brazilian termites, and then compared these values with those from other species of termites, ants and 22 other species of terrestrial invertebrates.  The tabular data include some species used as human food in various regions of the world.  Studier and Sevick (1992) reported the live and dry mass, water content, nitrogen, sodium, potassium, magnesium, calcium and total iron concentrations for representatives (mostly adults) of 16 orders of insects (360 species) occurring in south-central Michigan.  The tabular data include families and a few genera and species that are used somewhere as human food.  The authors report that, compared to published nutritional requirements (when meeting caloric requirements) for growth and reproduction in birds and mammals, insects are excellent sources of nitrogen, potassium and magnesium, highly variable sources of sodium and iron, and, rarely, adequate calcium sources.  The book by Slansky and Rodriguez (1987) is a valuable source of information on the nutritional ecology of many insect groups that are important as human food.

            Whole dried insects are about 10% chitin, a carbohydrate polymer found in invertebrate exoskeletons, protozoa, fungi and algae.  The chitin presents problems of digestibility and assimilability in monogastric animals, but it, and its derivitives, particularly chitosan, possess properties that are of increasing interest in medicine, industry and agriculture.  Goodman (1989) listed some of its capabilities: significantly reducing serum cholesterol, acting as a hemostatic agent, enhancing burn and wound healing, acting as an anticoagulant, protecting against certain pathogens in the blood and skin, serving as a non-allergenic drug carrier, providing a high tensile-strength biodegradable plastic for numerous consumer goods, enhancing pollutant removal from waste-water effluent, improving washability and antistatic nature of textiles, inhibiting growth of pathogenic soil fungi and nematodes, and boosting wheat, barley, oat, and pea yields as much as 20%. Investigators are calling chitin, with its abundance, toughness and biodegradable properties, the polymer of the future, according to Goodman.  While insects and fungi have the highest ratio of chitin to body mass and global bioproduction is enormous, the primary source to date has been waste products generated by the shellfish industry. From the foregoing account by Goodman, it seems apparent that if protein concentrates from insects become acceptable and produced on a large scale, the chitin byproduct could be of significant value.

            Ritter (1990) discussed cholesterol in insects.  Like other animals, most insects are approximately 0.1% sterol (i.e., 1 mg sterol/g tissue), but insects are unable to synthesize sterols de novo and must obtain them exogenously from the diet or from symbionts.  Ritter describes the metabolic conversion, or lack of conversion, of various sterols to cholesterol. Some insects, including edible species such as the honey bee, Apis mellifera, and the leaf-cutter ant, Atta cephalotes isthmicola, contain no cholesterol.  Through diet alterations in which the Δ5-sterols are replaced by other sterols, some other species, which are edible could be produced which contain little, if any, cholesterol.  Ritter's research has demonstrated this with the corn earworm, Heliothis zea, and it might be done, for example, with the cricket, Acheta domesticus, by feeding a diet rich in alfalfa sterols (i.e., Δ7-sterols).  

            DeFoliart (1991) reviewed the available data on insect fatty acids and reports that the proportions of saturated/unsaturated fatty acids are less than 40% saturated in most edible insects, grouping them with poultry and fish.  Another notable feature of insect fatty acids is the very high ratio of the polyunsaturates, linoleic and linolenic acids, higher in general than found in poultry and fish.

 

                                                                     Coleoptera

 

            McHargue (1917) conducted proximate and amino acid analyses on two species of insects, one of which was the June bug, Lachnosterna sp. (Family Scarabaeidae) (Phyllophaga = Lachnosterna).  It is stated that analysis showed "such a large percentage of protein present in the dry state," that further studies were conducted, but McHargue doesn't give the percentage found.  Data are presented on the amino acid content in comparison to beef roast and turkey white meat.  Lachnosterna was equivalent to the meats in lysine (8.02% of analyzed nitrogen), slightly lower in arginine (11.53%) and cystine (0.35%) and had only about 50% as much histidine content (6.57%).

            Davis (1918) noted that the grubs and beetles of Lachnosterna are eagerly preyed upon by numerous species of birds and mammals, particularly by crows and blackbirds.  Crows often follow the plough, eagerly picking all exposed grubs.  Davis cites the U.S. Biological Survey having found these insects in the stomachs of 78 species of birds and two species of toads.  Among native mammals, the skunk is probably the most valuable in eating qrubs.

            Farm fowls, especially turkeys but others also are fond of both grubs and adults, and the domestic hog "is the most efficient of all grub destroyers where it can be utilized" (Davis, pp. 12-13).  According to Davis, the practice of "hogging off" corn, thus saving the expense of harvesting and marketing, is a good preventive control for white grubs as well as cutworms, wireworms and other soil-infesting insects.  Advantages include not only (l) control of these insects, but (2) utilization of their food value, and (3) manuring of the land.

            Davis cites an example of control in which l00 pigs and 8 sows were turned into a heavily infested l0-acre cornfield in Illinois and destroyed 99% of the grubs within 27 days.  Assuming 34.6 grubs per hill (the number at the beginning of the experiment) and the number of hills per acre at 3,556, the pigs destroyed approximately l,217,083 grubs, or 11,278 grubs (24 lbs) per animal.  The pigs suffered no ill effects.

            Turkeys search diligently for grubs, and Davis states that he has seen infested timothy and sod fields thoroughly scratched up by these birds.  Chickens don't search unplowed fields but if allowed the run of the field during ploughing or cultivation they eagerly pick up every grub and beetle exposed.  Davis cites an instance in Iowa where a flock of about 150 chickens, encouraged to follow the plough, harrow, and cultivator, practically eliminated the grubs in a badly infested 15-acre field.  Davis notes that portable poultry houses have been used in Europe to allow foraging for the European May-beetle grubs.

            According to Davis, there are no authenticated reports of harmful dietary effects on either hogs or poultry from feeding heavily on grubs or adult beetles.  European tests revealed no difference in taste of eggs from grub-fed hens and others; in fact, the former had better yolks "for thickening and were worth three of the others to color sauces."  The only unfavorable result was "in the case of dried beetles mixed with bread and potatoes, which proved too exciting for the older fowls."

            Davis notes objections raised to the use of hogs, mainly to pasturing on sod land: l) Need for hog-tight fences - Davis believes the cost is quickly recouped through the value of the grubs as feed; 2) Rooting up of pasture land - to which Davis says the overturned sod reseeds itself the following season with no ill effect other than a roughing of the surface, which is of little significance; 3) Possible infection with the giant thorn-headed worm, Echinorhynchus gigas, an intestinal parasite of hogs, and of which the white grub is an intermediate host. According to Davis, there is no problem in fields where hogs have not pastured within the past three years.  Brood sows should be prevented from running in fields that are likely to contain infected grubs and in which hogs have pastured within the previous season or two.  Less care is needed relative to hogs being fed for market as they will probably be slaughtered before the worms become damaging.  Davis (pp. 23-24, his Fig. 14) provides a three-year schedule for using hogs to harvest grubs and prevent crop damage.  Davis states that there is an average of 106,680 grubs per acre in infested areas, and that their weight during the fall of their destructive season averages 1 gram (adults weigh slightly less); thus an infested acre contains approximately 235 lbs of grubs.  Davis (pp. 3-11) provides information on taxonomy, life cycles, etc.

            Finally, Davis presents the results of proximate analyses (% of fresh weight) of Lachnosterna grubs and beetles (p. 20):

 

                                                               Grubs           Adults

            Moisture                                        70.0             60.4

            Crude fat                                          3.1              4.0

            Crude protein                                 11.1            20.1

            Crude fiber                                       1.6              8.7

            Crude ash                                         2.0              1.6

            N-free extract

          (carbohydrates)                                   2.3              0.3

 

            Cotton and St. George (1929, p. 4) summarized the early use of the meal worm, Tenebrio molitor (Family Tenebrionidae), as animal feed, stating that it was introduced into Chile solely for rearing the larvae as bird feed.  In aquariums and zoological parks, they were in great demand for feeding small birds, amphibians, reptiles, insect-eating mammals, fish and carnivorous arthropods.  According to Cotton, a fish-bait vendor told him that "he could use 'half a billion' of them [mealworms] annually."  Cotton cites early references, as early as 1721, on their use as bird feed in Europe and summarizes his own extensive biological studies on rearing them.

            Fleming (1968, pp. 3-4) notes that many native birds and mammals feed readily on adults of the Japanese beetle, Popillia japonica Newman (Family Scarabaeidae).  He cites a U.S. Bureau of Biological Survey report in which stomach contents of 16 of 31 species of birds examined contained beetle remains.  Grackles ate more than other birds; all 29 grackles examined had eaten beetles and the beetles constituted 66% of their stomach contents. Chickens, turkeys, ducks and guineas feed readily on beetles and these along with the grackle, European starling, crow and gull (Larus spp.) dig up and devour large numbers of grubs in heavily infested areas, especially when fields are being plowed and grubs are close to the surface in grasslands.  Among native mammals, skunks are the most diligent predators of the Popillia grubs.  The common toad (Bufo lentiginosus) eats many beetles.  Hogs have long been known to gorge themselves on grubs.

            Fleming cites three sources in stating that proximate analyses of the beetles revealed 67.4% moisture, 22.1% protein, 2.1% fat, 1.5% ash, 6.6% crude fiber, and 0.3% nitrogen­-free extract.

            With space flight as well as planet-side food production in mind, Kok (1983) proposes to apply automated industrial technology wherein substrate is converted to insects in a manner similar to single cell protein production.  He explores several possible system types and operating methods using the concept of packed beds for insect incubation, growth and reproduction and concludes that the concept is feasible. The drug store beetle, Stegobium paniceum, is the experimental animal used in the investigation.

            Kok et al (1988) report that it is technically feasible to mass-­produce insects for human consumption by using industrial methods.  The test organism was Tribolium confusum (the confused flour beetle).  The authors describe a semi-continuous process based on the use of a single, batch-fed plug flow reactor and three basic unit operations.  The material passed through the reactor in four streams of small, segregated batches with a phase lag of 2 days between them.  The reactor performed four major functions corresponding to the four streams; 1) feed conditioning, 2) feed conversion, 3) dormant stage incubation (eggs, pupae) and 4) propagation (egg production).  The process consists of two major "cycles," conversion and propagation.  The three unit operations are sifting, air classification and solids mixing.  Bread, sphagetti sauce and hot dog weiners were prepared with the product pupae. These were found to be palatable by volunteer consumers.

            Kok et al (1991) report the results of opportunistic sampling of the system described in previous papers.  Samples were analyzed for moisture, ash, protein and fat, and mass balances were then calculated for these components.  Carbohydrate was found by difference.  The objectives of nutrient incorporation and fat generation were partially met, but overall yield of the process was rather low, according to the authors. "Process losses were dominated by losses incurred during the organism propagation cycle; nitrogen was lost in organism wastes such as larval exuvia."  Results of the study will be used in designing a second generation process.  

            Weissling and Giblin-Davis (1995) tested several artificial diets as alternatives to decomposing pineapple for culture of Rhynchophorus cruentatus (Fabr.) larvae.  The most suitable diet for larval growth and survival was a combination of canned pineapple, oats, sucrose, molasses, brewers yeast, Wesson's salts, vitamins and preservatives.  Poor growth and survival were obtained on diets not supplemented with brewers yeast. It was found that larvae would construct a cocoon only when placed in sugarcane stem. Sugarcane appeared to contribute little to continued growth of maturing larvae and probably is nothing more than a source of fiber for construction of the cocoon.  Although the motivation for this study pertained to the vector potential of R. cruentatus for the red ring nematode, Bursaphelenchus cocophilus, the authors state:

 

            . . . although we are aware of no human consumption of R. cruentatus larvae in the U.S., larvae of R. palmarum, R. phoenicis, and R. ferrugineus . . . are considered delicacies by some [in Africa, Asia, Latin America].  The culture of R. cruentatus on artificial diets could be a potential advancement in developing a niche for consumption of our indigenous species by palm weevil gourmets or feeding burrowing owls in captivity.

 

The authors note that, unlike some other Rhynchophorus species, R. cruentatus is not considered a major pest of palms, but it will attack transplanted or otherwise stressed ornamental palms; in Florida it is sympatric with the native cabbage palmetto, Sabal palmetto, which, because of its low cost, natural abundance, and high transplanting survivorship, is often used as mature specimens in landscaping.

  

                                                                        Diptera

 

            In situations where poultry manure is not usable as fertilizer in the immediate vicinity where produced, its disposal poses problems of odor, fly production and N contamination of soil and water.  Various fly species have received experimental attention for their ability to recycle poultry and other animal manures into useful feed products for poultry and livestock. Hodge (1911) calculated that a pair of house flies, Musca domestica L. (Family Muscidae), starting in April could produce enough progeny by August, if all survived, to cover the earth with a layer of flies 47 feet deep.  Although, as pointed out by DeFoliart (1975), this is an ecological absurdity, it does indicate the tremendous reproductive potential of some insects. Lindner (1919) appears to have been the first to suggest that house fly larvae might be used to recycle organic wastes, human waste specifically, to produce protein and fat as a useful byproduct.

            Rodriguez and Riehl (1959) conducted an experiment to determine whether cockerels could provide fly (Musca domestica) control in manure under chickens housed in wire cages off the ground.  They described their rationale thusly:

 

            Young chicks instinctively scratch and search every bit of surface within their reach constantly and industriously looking for food.  If growing chicks were allowed to scratch in the droppings under the wire cages, would their activities control flies?  If they did, what management practices would be useful in obtaining optimum performance?

 

Impressive control of M. domestica breeding was demonstrated in a flock of 200 chickens using one cockerel per 10 hens in cages. In four instances larvae were found in spots where the manure was very wet and hard for the chicks to work; no pupae were ever found, however, suggesting that larvae which the chicks did not find in the manure were caught as they left to seek dryer areas for pupation.

            In followup research, Rodriguez and Riehl (1962) demonstrated control of flies (M. domestica) by use of cockerels on commercial poultry ranches in southern California. They reported reductions to zero, in some cases, of fly larvae and pupae in chicken manure under cages with a raised wire mesh floor when cockerel chicks were released on the ground.  Control was maintained with ratios of 20 to 100 hens in cages per one cockerel on the ground.  The authors describe management practices favorable to successful fly control by the chicks.  In the laboratory, baby chicks only 1-2 days old were found to peck instinctively at larvae and pupae although they were unable to pick them up.  At 3 days of age the chicks ate 100 larvae or pupae per chick per day and by 15 weeks of age were averaging 8,000 or more per day.  The consumption of the flies (200 g/day) was higher than the consumption of mash or grain on a free-choice basis.  Under ranch conditions, feed was supplied in the evening for the first few days but not thereafter unless fly breeding was completely eliminated.  At a rabbitry with 175 rabbits, control of fly larvae and pupae was obtained with one cockerel per five rabbits.  

            Calvert and colleagues at the U.S. Department of Agriculture were one of two groups which began research in the late 1960's on the use of M. domestica for recycling poultry manure into a high-protein feedstuff for poultry.  Calvert et al (1969a) analyzed pupae produced in CSMA fly medium and found a crude protein content of 63.1% and fat content of 15.5% (Table 1; see authors' Table 1).  Amino acid analysis indicated a protein quality similar to that of meat and fishmeal; fatty acid analysis showed a pattern similar to that of some fish oils, although the pupal fat content was higher.  Ash content was lower than that of fish meal.  When house fly pupae were incorporated into a practical chick starter diet, replacing soybean meal, the chicks gained significantly more weight than chicks fed the soybean meal diet during a two-week experiment.  The increase in weight gain was due to an increase in feed consumption as feed-to-gain ratios were similar in the two qroups.

            Relative to recycling poultry manure, Calvert et al (1969b) reported in a brief abstract that fresh hen excreta will support a density of 3 pupae per gram at temperatures of 23 to 26 C, and at this density the feces loses about 20% more moisture than feces without pupae.  With a moisture content of only about 46%, the feces is loose, crumbly in texture, and essentially odorless.

            Calvert et al (1970) presented data to support the seeding rate of 3 eggs per gram of fresh excreta as the optimum seeding rate, and described equipment designed to simplify collection of pupae from the processed excreta. A seeding rate of 1.5 eggs per gram of excreta produced the largest pupae (ave. of 16.5 mg), highest survival (85.1%), and a total pupal weight of 4.23 g from 200 g of excreta in 8 days.  A seeding rate of 4.5 eggs per gram of excreta yielded the smallest pupae (10.0 mg), lowest survival rate (44.4%), and lowest total pupal weight (3.87 g) (although this seeding rate did result in the greatest loss of moisture and thus weight, as well as nitrogen reduction in the fecal samples). At a seeding rate of 3 eggs per gram of excreta (the rate selected as best), pupal weight averaged 12.0 g, survival 66.4%, and total weight of pupae 4.55 g.

            Regardless of seeding ratio, odor was reduced to an unobjectionable level within 4 days, and the excreta were reduced to an essentially odorless, friable material within 8 days.  The investigators suggest its use, with additional drying and pelleting, as a soil conditioner.  The pelleted material was found to disintegrate rapidly with the addition of water, and without renewing the obnoxious odor of the fresh excreta.

            Morgan et al (1970) re-described and illustrated the pupal harvest apparatus described previously by Calvert et al (1970) (Fig. 1; see authors' Fig. 1).  Fresh poultry feces, 10-12 lbs, were placed in the center section of the top box to a depth of 2.5 to 3 inches; the narrow side sections served as air vents for release of the ammonia accumulating below.  The device was kept lighted from above to prevent the negatively phototactic larvae from wandering upward in search of pupation sites.  By the sixth day, at 68-80° F, most of the larvae had passed through the 1/8-inch hardware cloth floor to the tray below and wriggled through the l/16-inch fiber-glass screen to the solid floor to pupate.  The few particles of fecal material that dropped through the hardware cloth were retained on the fiber qlass screen.

            Morgan et al note that the excreta of White Leghorn laying hens average 0.25 to 0.40 lbs/day.  Thus, the daily production of 100,000 layers ranges from 12.5 to 20 tons and creates an enormous disposal problem resulting from odor and water pollution.  Morgan et al believe that, from the excreta of 100,000 hens, 500 to 1,000 lbs of pupae can be produced daily while reducing the excreta to a semi-dry, crumbly waste suitable as a soil conditioner.

            Calvert et al (1971) conducted analyses and feeding trials to determine the value of newly emerged house flies as a protein source for chicks.  The fresh flies contained 69% moisture; the dried material contained 75% protein and 7% fat.  In feeding trials to 3 weeks of age, the fly meal slightly improved chick growth and there was little difference in feed/gain ratios compared to chicks fed a soybean meal diet.  Thus, the adult house fly is also a good protein source for the young chick. These investigators also tested the digested manure for chick growth, but growth was substantially less than for chicks fed the soybean meal diet.

            The second group initiating research on the house fly in the late 1960's was at Colorado State University.  In a brief abstract, Miller and Shaw (1969) state that of five species tested for their ability to grow and reproduce in fresh poultry manure, Musca domestica and Muscina stabulans (Muscidae) were most promising.  M. domestica developed from egg to pupa in 5­6 days at 37° C.  The larvae removed about 80% of the organic matter from fresh poultry manure, and reduced the moisture content of the manure from 75% to 50% in 5-6 days.  No experimental methods are described in the abstract.

            Miller (1969) discusses the disposal problem, pointing out that fresh manure is heavy, containing about 75% water, and that the labor needed to move it from points of accumulation prohibits its use as a fertilizer.  Such manure accumulations offer breeding sites for wild flies, thus creating a sanitation problem.  Miller briefly describes methods of managing the fly breeding colony and harvesting pupae, presents tables of data on proximate and amino acid analysis and mineral content of dried fly pupae, weight gains and feed efficiency on broiler diets containing fly pupae, and analysis of fresh and digested manure, but gives no experimental methodology.

            Leinati et al (1971) reported that infestations of Hypoderma sp. (Hypodermatidae) in the backs of cattle on mountain pastures can be reduced by allowing cattle and poultry (chickens and turkeys) to graze together on the same pastures.  The poultry devour grubs after they drop to the ground for pupation.

            Teotia and Miller (1970a,b) presented brief abstracts of work that was published in full later.  Teotia and Miller (1973a) describe methods of managing the breeding colony, conducting larval density, humidity and temperature studies, pupal harvest (by flotation), and production under caged layers.  They found the best seeding rate to be 3 g of fly eggs per 4 kg of fresh manure (Table 2; see authors' Table 1]) at 27 C and 41% RH.  This seeding rate resulted in the highest total weight of pupae harvested (76 g), highest percentage of manure lost in digestion (51.3%), and lowest weight of manure harvested (1,949 g).  It took 8 days at 27°C and 41% RH.  At these temperature and humidity conditions, moisture in the manure was reduced from 78.5% to 55.0% by the aerating action of the larvae and decomposition of the manure.  Teotia and Miller also used fly eggs and/or larvae seeding to digest the manure under caged birds.  This worked fairly well, but temperature must be kept above 20 C or larval development is inhibited.

            Teotia and Miller (1974) conducted proximate and amino acid analyses on house fly pupae and obtained values similar to those of Calvert et al (1969) except that fat content was lower and ash content higher than in the former study.  These differences may have been due to the different rearing media employed, Teotia and Miller rearing their larvae in poultry manure while Calvert et al used CSMA fly medium.  In the feeding trials, day-old single comb white leghorn chicks were fed to 4 weeks of age on house fly pupae with or without addition of a B vitamin and trace mineral supplement.  Final body weights and feed/gain ratios of chicks fed the experimental diets and the soybean meal control were not significantly different.  Unfortunately, the fact that the house fly pupae were merely substituted for soybean meal made the diets neither isocaloric nor isonitrogenous, which makes a direct comparison impossible.  It appeared, however, that the pupae were a good source of B vitamins and trace minerals.  The authors also conducted proximate and mineral analyses of fresh and digested manure.  In feeding trials with manure containing pupae, chick growth was comparatively poor on the digested manure/pupae mixture.

            Teotia and Miller (1973b) conducted a second set of feeding experiments in which the flaws in the first experiments were corrected by adjusting the levels of the other dietary ingredients so that the experimental and control diets were isocaloric and isonitrogenous.  Also, fast-growing broiler chicks were used which should be more sensitive in detecting differences in protein quality.  Lastly, this trial was of 7 weeks' duration as opposed to 4 weeks in the earlier experiments.  As before, the experimental diet was not supplemented with a B vitamin or trace mineral mix.  After 7 weeks there were no significant differences in weight gain or feed/gain ratios between the two treatments. Unfortunately, the protein content of the diet was kept constant throughout the experiment and since the NRC (1977) requirement for broiler chicks changes from 23% at Day 1 to 18% at 6 weeks of age, the ability of this experiment to detect anything but a major difference in protein quality was compromised.

            Miller et al (1974) provide a summary table (Table 3; see authors' Table 2) showing results of digestion of fresh poultry manure at a seeding rate of 1.0 g of fly eggs/kg of manure.  Approximately 80% of the organic matter was used by the larvae during their development.  About 58% of the moisture was lost while mineral content was not changed.  The manure residue contained about 15% protein after pupae were removed.  Physically, the manure was somewhat granular and could be dried readily because of the increased surface area, small particle size and improved aeration.

            Hale (1973) reported that dried larvae of the soldier fly, Hermetia illucens (L.) (Family Stratiomyidae) contained 45.2% crude protein and 31.4% ether extract.  Amino acid analysis showed the larvae to be higher in methionine (1.9% of crude protein) than either soybean meal or meat scraps (both 1.4%). In a two-­week feeding trial, there were no significant differences in weight gained or feed/gain ratio of chicks fed a diet containing either dried Hermetia larvae or soybean meal as the major protein source.  The chicks fed the soybean meal diet consumed significantly more feed, however.  The author speculates on several possible causes for the apparently lower palatability of the larval diet: high content of larval meal (35% of the diets were composed of larval or soybean meal, respectively); somewhat higher fat content in the larval diet (chicks on the soybean meal may have compensated by consuming more total feed); and, higher crude fiber content in the larval diet.

            Hale notes that H. illucens larvae are large, full-grown larvae averaging about 250 mg in weight compared to about 25 mg for house fly pupae.  The larvae are found in a variety of moist situations high in organic matter, such as decaying fruits and vegetables, damp feed grains either ground or whole, and animal wastes in and near animal quarters.  About two weeks are required to reach maturity, and the larvae are very "hardy."

            Beard and Sands (1973) tested larvae of several species of Diptera for their ability to degrade both anaerobic and aerobic poultry manure.  They found that all species tested except Fannia canicularis (L.) (Family Muscidae) and unidentified species of Sphaeroceridae (small dung flies) failed completely in anaerobic manure.  Fannia and the sphaerocerids thrived in aerobic manure, but Beard and Sands concluded that their small size and their behavior limit their potential practical value in degrading manure.  The house fly, M. domestica showed the greatest adaptability for managed degradation of aerobic poultry manure, while larvae of several other species didn't grow well enough to warrant further investigation, i.e., Phormia regina (Meigen), Protophormia terrae-novae (Robineau-Desvoidy) and Phaenicia sericata (Meigen), all of the Family Calliphoridae, and Sarcophaga bullata Park (Sarcophagidae).

            Beard and Sands provided data on a number of factors affecting degradation of poultry manure by the house fly. 1) Genetic variability offers the opportunity of selecting strains that are better degraders of manure.  Seven strains were evaluated on the basis of mean survival-size scores, including two flightless strains, but none were better than the strain already adapted to the laboratory. 2) There appeared to be no difference in fecundity (and therefore dietary protein for egg development) between sugar/manure-fed flies and sugar/milk-fed flies. 3) When offered a choice between manure and dog food moistened with yeast suspension as an oviposition medium, flies discriminated against manure, but in the absence of a better alternative, manure was acceptable. 4) Measured by survival-­size score, dog meal-yeast medium was slightly better (significant at 5% level) than manure as a larval development medium. 5) Size-survival scores showed that flies do better (larvae) in fresh than in aged manure. 6) Rate of oxygen consumption is a gross measure of metabolic activity of organisms growing in manure.  Oxygen was utilized at essentially the same rate by manure with larvae alone, with microorganisms alone, or with both. 7) Bacteria rather than fungi appear to be the dominant constituents of manure microflora.  Some bacteria may be detrimental to larval development while yeasts appear to play a minor role as a dietary source for larvae. 8) Although larval activity reduced N, anaerobic decomposition did also, almost to the same degree.  This and the results of respiration studies suggest that larvae share manure nutrients with microorganisms and that reduction of N levels is not solely attributable to larvae.  The main contribution of larvae appears, therefore, according to the authors, to be mechanical aeration resulting in increased loss of ammonia, water vapor, and other gases; hence favoring aerobic organisms, eliminating offensive odor, and dehydrating the medium.  The authors discuss these and other factors as they interrelate in manure degradation.  Pupal harvest by flotation isn't good because it doesn't retain the dry condition of the residual manure.  The authors suggest that hens could be used to pick larvae and pupae from the manure.

            Papp (1975) conducted experiments to determine the economic feasibility of processing pig manure by house fly larvae. Production yields were as high as 8.05% compared to a theoretical maximum of 10%, results considered equivocal by the author.

            Chemical assays by Dashefsky et al (1976) showed pupae of Musca autumnalis DeGeer (Family Muscidae) to contain a high percentage of phosphorus, 5.73% of dry weight.  In a 15-day feeding trial, the phosphorus was found to be at least 92% biologically available to White Rock chicks, making the pupae at least of the same quality as most of the commercially sold dicalcium phosphate sources.  Analysis of dried pupae meal revealed a crude protein content of 46.5%.

            Newton et al (1977) conducted a digestion trial on 5-week-old barrow pigs to evaluate dried, ground soldier fly larvae, H. illucens, as a dietary supplement compared to soybean meal.  The larvae were collected from cattle feces and urine slurry.  Proximate composition and calcium and phosphorus  content of dried larvae was 7.9% moisture, and, on a dry matter basis: crude protein 42.1%, ether extract 34.8%, crude fiber 7.0%, NFE 1.4%, ash 14.6%, calcium 5.0% and phosphorus 1.5%, respectively (see authors' Table 2 for these data and data on digestion trial diets).  Apparent digestibilities for the larval meal diet and (in parentheses) the soybean meal diet were: dry matter 77.5 (85.3), nitrogen 76.0 (77.2), ether extract 83.6 (73.0), crude fiber 53.8 (49.2), ash 45.2 (61.7), NFE 84.7 (91.2), calcium 38.9 (39.3), and phosphorus 24.5 (51.3).  Values for dry matter, nitrogen, ash and NFE were significantly greater (P <.05) for the soybean meal diet than for the larval meal diet. Pigs did not discriminate against the larval meal diet, indicating good palatability.  The authors conclude that further studies are needed to determine the optimum levels of larvae in livestock diets.  Larvae would be especially valuable for their amino acid, ether extract and calcium content, but because of the high ash and ether extract content might be better utilized at lower levels than those used in these trials.  Booram et al (1977) reported the results of additional investigations on the recycling of swine manure by H. illucens.

            Calvert (1977) reviewed the use of both unicellular organisms and invertebrates for protein production from animal and municipal wastes, including algae, yeasts, fungi, mixed cultures of bacteria, house fly larvae and earthworms.

            Ocio et al (1979) provided proximate and amino acid analyses of house fly larvae grown in municipal organic waste (MOW).  Feed trials were conducted with three diets that were isocaloric and isonitrogenous: 1) standard corn-soy diet, 2) fish meal substituted for some of the soybean meal so that 9% of the dietary protein was from fish meal, and 3) house fly larvae substituted for some of the soybean meal such that the larvae furnished 12% of the dietary protein.  There were no significant differences in weight gain or feed/gain ratio in birds from any of the three treatments after 4 weeks.

            Abdel Gawaad and Brune (1979) tested a mixture (1:1) of dried, ground larvae of Phormia regina (Family Calliphoridae) and M. domestica as the high-protein source for broilers fed through the fourth week of age.  Amino acid compositions of the two fly species were similar (data are given by the authors).  Lysine content of the larvae-meal was high, even higher than in fish meal, but methionine was low.  There were no significant differences in final weight or feed conversion efficiency of chicks fed the experimental larval meal diet and the control chicks fed the soybean meal diet.  The investigators observed a significantly lower weight of feathers in the larval-fed group, which they suggest may have resulted from the low methionine in the diet.  As to carcass composition, the dry matter content of the breast muscle and the drumstick of the test animals was significantly greater than in the controls, which the authors attribute to a significantly higher fat deposition, while protein accumulation was lower in the test animals.  The ash content in the meat and bones showed no marked difference.  In an organoleptic test on the stewed breast meat, no marked effect on color, smell or taste could be detected.

            Abdel Gawaad and Brune mention a rearing procedure (not yet published) whereby one pair of flies supposedly produces 190 billion flies from April to September; based on a fresh weight of 0.023 g per full-grown larva, this would total 4.4 x 106 kg fresh weight or 1.2 x 106 kg dry weight, and about 0.6 x 106 kg of protein.

            Koo et al (1980) conducted studies on the face fly, Musca autumnalis (De Geer), reared in cattle manure and allowed to pupate in sand.  The authors point out three biological advantages of this insect over the house fly: 1) It's larger in size, face fly pupae averaging .03 g compared to .025 g for house fly pupae; 2) Pupation occurs in 3 days following oviposition at 41°C compared to 5-6 days for the house fly; and 3) Adult house flies are subject to epidemics of infection with the phycomycete Entomophthoro muscae while there is no record of face flies succumbing to this fungus.  At the conclusion of feeding, face fly larvae, like most other flies, void the intestine and seek a drier location in which to pupate making it easy to harvest the pupae free of the manure in which the larvae have fed.

            Proximate analysis revealed 51.7% crude protein in the face fly pupae, which is less than that found in house fly pupae. Crude fat content was intermediate compared to reported values for the house fly while nitrogen free extract and fiber were less than in the housefly.  Interestingly, face fly pupae contained 3 times as much calcium and twice as much phosphorus as reported for house fly pupae.  In feeding trials using Single Comb White Leghorn chicks, in which dried pupae were directly substituted for soybean oil meal to 4 weeks of age, there was a slight decrease in feed efficiency which the authors attribute mainly to the lower gross energy value of the pupal meal (4.284 kcal/g) compared to the soybean meal used (4.682 kcal/g).  Microbial counts of the dried pupae were well below the tolerances for human food as given by Powers (1976). The authors conclude that dried, ground face fly pupae are a suitable source of protein in poultry diets and that, microbiologically, they would be acceptable for human consumption.

            In feeding trials with channel catfish and blue tilapia, manually collected black soldier fly larvae (H. illucens) from poultry waste have shown promise as a feed ingredient for commercial fish production (Bondari and Sheppard 1981). Taste tests showed that the fish fed soldier fly larvae are acceptable to the consumer.  The authors note that, because the larvae of this species can be produced from a wide variety of waste materials, "production of larvae on a large-scale basis for fish and animal feed will also have an impact on recycling of waste products."

            Tests in an experimental caged layer house demonstrated that soldier fly larvae (H. illucens), in addition to offering a potential food source, provide house fly and lesser house fly control and about a 50% reduction in manure volume (Sheppard 1983).  The rate of self-collection by the larvae indicated that a commercial operation with 20,000 hens could harvest 540 kg of mature larvae per month during the summer.

            E1 Boushy et al (1985) discuss limitations inherent in the value of dried poultry manure (DPM) as poultry feed and suggest (with a review of the pertinent literature) that the use of organisms to break down the excreta, such as house fly larvae, earthworms, or by means of fermentation, or upgrading by aerobic digestion and oxidation ditch or algae culture are ways of converting the manure to a protein source in animal diets.  In DPM only about half of the total nitrogen is true protein, the remainder being in the form of uric acid which cannot be utilised by fowl and may even be toxic at levels above 1.07% in the ration.  The low available energy in DPM is also a problem. Relative to biodegradation of poultry manure by house fly larvae, E1 Boushy et al note from literature sources that the digested manure residue and pupae contain a high level of protein but a low level of non-protein nitrogen. Pupal yields are 3.2% of the fresh manure and about 4.0% on a dry matter basis.  The authors discuss the technological aspects of the different systems of handling poultry manure, focusing on both the advantages and disadvantages of each. For comparison of earthworms and pupae, the two main sources cited by E1 Boushy (Fosgate and Babb 1972 and Calvert 1977) should also be consulted.

            E1 Boushy (1986) provides numerous tables and data on the world food supply and diets in the developing countries, stating that diets of the inhabitants are generally sufficient in calories, mainly from vegetable sources, and short in animal protein.  Increased consumption of poultry is suggested as the best solution, considering that poultry meat is most palatable and broilers are fast-growing, reaching a weight of 1.5 kg in 7 weeks with a food conversion of 1.8.  The total volume of broiler meat produced in developing countries is estimated to be 7 million metric tons per year, providing an estimated consumption of 3 kg per capita per year. E1 Boushy advocates the development of local industries, as opposed to home slaughter, partly because of better utilization of byproducts such as manure and offal, leadinq to the establishment of secondary rural industries.

            According to E1 Boushy, poultry in the developing countries produce about 40.3 million metric tons of manure per year, about 26.2 million tons of it from layers and 14.1 million tons from broilers.  The use of dry poultry waste as feed for ruminants, aerobic fermentation, or biodegradation of the manure with organisms such as fly larvae or earthworms are ways of upgrading the manure to supply feed products. In the case of house fly pupae, based on a yield of 3.2%, a metric ton of manure can be converted to 32 kg of high-protein feedstuff.  This compares to 13.3 kg of dried earthworms per ton.  The total of 40.3 million metric tons per year could thus be converted to l.3 million tons of fly pupae.

            Glofcheskie and Surgeoner (1990) investigated the usefulness of Muscovy ducks in an integrated program for control of house flies (M. domestica).  In laboratory trials, ducks removed adult house flies at least 30 times faster than commercial bait cards, coiled fly paper rolls, fly sheets, or fly traps.  The LT90 for ducks in 0.24m3 cages with 100 flies was 0.6 h compared to 15.3 h for the most effective commercial device.  In pens with calves, ducks survived for test periods of 12 weeks or more without injury or feed supplement, and ingested a mean of 25 flies per 15-min observation period when populations were low to moderate.  The observed behavior is innate, suggest the authors, as the experimental ducks had no previous experience with flies, yet fed on them readily even when provided feed ad lib.  One of the ducks penned with a calf was observed to capture, on average, 23 flies per 32.5 attempts.  Two (among several) advantages of ducks were effectiveness against insecticide-resistent flies and elimination of breeding sites by removing spilled feed. The ducks were also more economical than the commercial control devices.  The authors estimate that under their local conditions a producer could make a profit of $65 on 10 ducks by selling them at the end of the season, while the other control devices range in cost from $171 to $455 for season-long fly removal.

            At a midsize dairy farm that kept unrestrained Muscovy ducks for fly control, the ducks stayed in the vicinity of the barn and interacted well with animals and humans.  In addition to feeding on adult house flies, they also picked flies from the lower legs of cows, indicating that they were also feeding on stable flies,    Stomoxys calcitrans (L.).  The investgators caution that ducks cannot be used in commercial poultry operations because of disease hazards.

            El Boushy (1991) points out that a chicken ranch with 25,000 caged layers produces 2500 kg of wet manure per day or 912.5 tons per year, thus creating a major problem of waste disposal.  Dry poultry manure is not, of itself, recyclable as a good feedstuff for poultry because of its low energy and high content of uric acid and non-protein nitrogen, neither of which can be utilized by monogastric animals.  Research during the late 1960s and the decade of the 1970s, however, showed that house fly (Musca domestica) pupal meal produced by larval biodegradation of poultry manure is of high protein quality.  In addition, digestion of the manure by larvae converts it into an odorless, loose, crumbly product that can be easily dried and used as a feedstuff.  Unfortunately, no practical large-scale method of separating the pupae from the digested manure residue has been found.  El Boushy suggests then that the most practical procedure is to produce a mixture of pupae and manure residue, thus upgrading the latter to reasonable feedstuff quality.  He describes how this could probably be economically accomplished with equipment that is already in practical use on many large poultry farms.

            Studies on the soldier fly, H. illucens, appear to have solved the problem of efficient harvest of pupae from manure under caged layers (Sheppard 1992, Sheppard et al 1992). This non-pest species is proving to be an excellent manure management agent that can produce large quantities of high-quality animal feedstuff, almost completely prevent house fly development and reduce manure residue volume by 50%.  Prepupal soldier flies are self-collected as they crawl out of the manure basin seeking pupation sites.  They crawl up a 40° slope on one wall of the basin, into a 1/2 inch slit in a 15 cm diameter PVC pipe at the top of the slope, then crawl to a container at the end of the pipe (in the experimental facility, they negotiated a 12-meter length of pipe).  The authors estimate that the value of the dried larval feedstuff produced, savings in the cost of insecticide and manure removal and surface application would net a small 20,000 hen egg producer an extra US $7,360.  They state that the system should easily adapt to swine waste management, and that soldier flies could be used to degrade many other organic wastes.

            In a second report on use of Muscovy ducks for fly (M. domestica) control, Glofcheskie and Surgeoner (1993) found that, in fly-proof calf pens, one duck per pen reduced adult fly numbers by 96.8% and larvae by 98.7% compared to pens without a duck.  In an enclosed calf room, fly reductions were 84% and 93% compared to times when ducks were not present.  In open areas of the dairy, however, which permitted immigration and emigration of flies, reductions were not statistically significant. Ducks reduced fly numbers on animals by 91% in an enclosed swine farrowing room and by up to 86% in an open dry sow house.  Female ducks were observed to consume flies up to three times faster than did males.  Ducks had access to flies, water and wasted feed, and duck health was maintained in most experiments without supplementary feedings.  At the end of the tests, the least valuable ducks were sold for twice their original cost ($4 vs $2), and, in addition, cooperators saved $100 to $300 by not having to purchase fly control chemicals.  The authors emphasize that the use of ducks must be considered a supplement to good sanitation. They report that all of the cooperators indicated that they would use ducks in the following season.

            In a textbook based on the use of some neglected vegetable and animal wastes as a poultry feedstuff, El Boushy and van der Poel (1994) include a section on Dried Poultry Waste under which they discuss biological conversion of layer manure by means of house fly larvae, earthworms, aerobic fermentation, oxidation ditch and algae.

 

            Sheppard et al (1995) add to information on their manure management system using the black soldier fly. Their Abstract is duplicated below:

 

Indent margins

A manure management system for laying hens using the black soldier fly, Hermetia illucens (L.) converted manure to a 42% protein, 35% fat feedstuff, reduced manure accumulation by at least 50% and eliminated house fly breeding. No extra facility or added energy was required. Mature larvae self-harvested producing a feedstuff as they attempted to pupate. Optimal feedstuff to manure dry matter yield was 7.8%. This insect occurs worldwide in tropical and warm-temperature regions and can digest many biological wastes.

 

                                                                     Homoptera

 

            Hildreth (1830) described an emergence of Magicicada (= Cicada) septendecim (Family Cicadidae) (the "17-year locust") in 1829 in Ohio and mentions their attraction as food for animals: "Hogs eat them in preference to any other food; squirrels, birds, domestic fowls, etc., fattened on them.  So much were they attracted by the cicadae, that very few birds were seen around our gardens during their continuence, and our cherries, etc. remained unmolested."

            Marlatt (1907) lists more than two dozen species of native birds that feed on the periodical cicada.  He states that the English sparrow (Passer domesticus) is perhaps its greatest enemy, but several native species neglected other foods when cicadas were available.  Fox squirrels eat them and chipmunks (Tamias striatus) are very fond of them.  Cicada remains have been found in black bass, blue catfish and white sucker.  Marlatt cites a John Bartram that hogs rooted up the ground a foot deep in search of cicadas  and he quotes a Dr. Potter that great numbers are "devoured by hogs, squirrels, all kinds of poultry, and birds, which live and fatten on them."  Dogs become fond of them, according to a Dr. Phares (Marlatt, p. 104) who also reported that they were "said to have killed a few hogs in Amite County" in 1859.

            Cicadas can be collected by hand if it is done early in the morning or in late evening when they are somewhat torpid and sluggish.  Marlatt (pp. 141-142) states that if collecting is "undertaken at the first appearance of the Cicada and repeated each day, the work of control will be facilitated by the fact that most of the insects will be on young trees and within comparatively easy reach."  Work for the protection of nursery stock in Pennsylvania is cited in which more than 1,000 cicadas were collected per day per collector. Despite the collection of 70,000 cicadas over a period of more than two weeks, 05% of 240,000 peach trees were lost.