A variety of insects are commonly fed to captive insectivores. We review the nutrient content of a variety of commercially raised insects and compare those values to the data available for wild insects. These data are discussed in light of the nutrient requirements for domestic animals to identify nutrients of concern for captive insectivores. Additionally, various environmental and dietary factors that can significantly affect insect nutrient composition are reviewed. We then evaluate the various techniques that are currently used to enhance the nutrient content of commercially bred insects, including gut loading and dusting. Lastly, possible negative considerations that might be important factors when feeding captive insectivores, including pathogens, pathogenic microorganisms, toxins, and antinutritional factors, are discussed.

Insects as food for insectivores

Fruit flies are the most economically important group of phytophagous flies worldwide. Whereas the ecological role of bacteria associated with tephritid fruit fly species of the genera Bactrocera and Ceratitis has been demonstrated, the diversity of the bacterial community in Anastrepha has been poorly characterized. This study represents the first comprehensive analysis of the bacterial community in the gut of larvae and adults of Anastrepha ludens, A. obliqua, A. serpentina, and A. striata using 454 pyrosequencing. A total of four phyla, seven classes, 11 families, and 27 bacterial genera were identified. Proteobacteria was the most represented phylum, followed by Firmicutes, Actinobacteria, and Deinococcus-Thermus. The genera Citrobacter, Enterobacter, Escherichia, Klebsiella, and Raoultella were dominant in all samples analyzed. In general, the bacterial community diversity in adult flies was higher in species with a broader diet breadth than species with a restricted number of hosts, whereas it was also higher in adults versus larvae. Differences in bacterial communities in adults might be determined by the number of fruit species infested. Lastly, the predictive functional profile analysis suggested that community members may participate in metabolic pathways related to membrane transport and metabolism of carbohydrates, amino acids, cofactors, and lipids. These results provide the basis for the study of unexplored functional roles of bacteria in this insect group.

Comparative Analysis of the Gut Bacterial Community of Four Anastrepha Fruit Flies (Diptera: Tephritidae) Based on Pyrosequencing

The importance of various stages of the silkworm, Bombyx mori viz., eggs, larvae, pupae, moths and its products, by-products and waste products as a potential medicinal source has been indicated. Larvae have been identified as a possible source of adipokinetic hormone (AKH), chymotrypsin inhibitors, s- N -acetylglucosaminidase, sex pheromone bombykol, amino acids, etc., apart from their value as health food especially for cardiac and diabetic patients, bronchial asthma, primary trigeminal neuralgia, vocal nodules and polyps and in the treatment of facial palsy and pain. Pupae are a source of proteins, vitamin B 1, B 2 and E, diapause hormone, amino acids, etc., and form a part of antibacterial and antihistaminic preparations. Male moths are used to treat sterility. Paste chlorophyll, pectin, phytol, carotene and triacontanol, solanesol, etc., extracted from silkworm feces are used in the treatment of various diseases such as hepatitis, acute pancreatitis, chronic nephritis, stomach and gastric disorders, ...

Bombyx mori – A Review of its Potential as a Medicinal Insect

Because of an increasing world population, with more demanding consumers, the demand for animal based protein is on the increase. To meet this increased demand, alternative sources of animal based protein are required. When compared to conventional production animals, insects are suggested to be an interesting protein source because they have a high reproductive capacity, high nutritional quality, and high feed conversion efficiency, they can use waste as feed and are suggested to be produced more sustainably. This thesis starts with a historical perspective on insects as food and feed, and explains why insects are expected to be more suitable production animals. In Chapter 2 the nutritional quality of insects is discussed based on a variety of insects that are commonly used as feed or food. Additionally, various environmental and dietary factors which are known to significantly affect insect chemical composition are reviewed. In Chapter 3 the direct production of greenhouse gases (GHG) and ammonia, as well as carbon dioxide emission and average daily weight gain of five insect species is quantified. Differences regarding the production of GHGs (expressed as CO2 equivalents) between insect species were mainly due to the production of methane. All species tested emitted lower amounts of GHG than cattle, had a higher growth rate than cattle or pigs, and emitted lower amounts of ammonia and either comparable or lower amounts of GHG than pigs. Results from Chapter 3 were used in a Life Cycle Assessment conducted in Chapter 4. For a mealworm production system total GHG production, energy use, and land use were quantified and compared to conventional sources of animal protein. This chapter shows that mealworms should be considered a more sustainable source of edible protein, and that a large part of their environmental impact is due to the feed they consume. In Chapter 5 four diets composed from industrial organic by-products were formulated such that they varied in protein and fat content. These diets were offered to four insect species and their feed conversion efficiency was determined. Diets used in large scale production systems were included and served as controls. Diet composition affected feed conversion efficiency in all species. It is concluded that the four investigated species are efficient production animals and can therefore be considered interesting for the production of feed or food. Furthermore, diet composition affected insect composition, indicating possibilities to tailor the composition of these insects to best meet consumers’ needs. In Chapter 6 the suitability of chicken, pig, and cow manure was compared as feed for larvae of the Black Soldier Fly, which in turn could be used as feed for conventional production animals. Newly hatched larvae were directly inoculated on moistened manure. Whereas survival was high on all three tested substrates, the development time was greatly prolonged compared to the control diet. On pig manure, more nitrogen was utilised than on chicken and cow manure, while P utilisation was highest on cow manure. A large proportion of manure nitrogen was lost in all treatments, indicating that the production system would require a way to prevent this in order to make it ecologically sound. Furthermore, to improve economic viability, shorter development times would be required. In Chapter 7 the suggestions why insects would make suitable production animals are evaluated based on both literature data, and data gathered in this thesis. Furthermore, prospects for insects as food or feed are put forward, with emphasis on the knowledge and legislation requirements for the further development of the insect production sector.

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Insects as food and feed: nutrient composition and environmental impact

A variety of commercially raised insect species are commonly fed to captive insectivores. We review their nutrient content and compare those values to the data available for wild-caught insects. These data are discussed in light of the nutrient requirements for domestic animals to identify nutrients of concern for captive insectivores. Additionally, various environmental and dietary factors which can significantly affect insect nutrient composition are reviewed. We then evaluate the various techniques that are currently used to enhance the nutrient content of commercially bred insects including gut loading, dusting and modifying the composition of the insect through dietary changes. Lastly possible safety considerations including pathogens, pathogenic microorganisms, toxins, and antinutritional factors that might be important factors when feeding captive insectivores are discussed. 

Chrysalis oil, an insect fat obtained from the spent silk worm pupae, Bombyx mori, is a by-product of sericultural industry and represents a potential source of 1750 tons of linolenic-rich oil per annum for India. Fatty acid and triglyceride compositions of chrysalis oil have been determined by the combination of the techniques of lower temperature segregation, lipolysis, thin layer and gas liquid chromatography. Percentage contents of the component acids are: C14:0, 0.6; C16:0, 19.3; C18:0 3.9; C18:1, 17.7; C18:2, 9.8, and C18:3, 48.7. Major component triglycerides are, LLnLn, 5.2%; PLnO, 6.4%;OLnLn, 9.6%; LnLnLn, 10.5% and PLnLn, 14.0% (P, palmitic; O, oleic; L, linoleic and Ln, linolenic acids. On low temperature crystallization, Chrysalis oil yielded two fractions amounting together to 40% of the total with composition quite similar to that of linseed oil.

U. K. Majumder

Papers

Triglyceride composition of chrysalis oil, an insect lipid