Excerpts from:  “Nutritional Diseases” by H.L. House, in Insect Pathology, vol. 1, Academic Press, 1963.

“In insects, as in other animals and in plants, nutritional diseases develop when faulty nutrition causes the metabolism of the organism to become abnormal.  The importance of these diseases and the close interrelation between faulty nutrition and deranged metabolism were recognized by Steinhaus (1949) in his “Principles of Insect Pathology”.  As might be expected, determinations of the specific causes and manifestations of these diseases come mostly from nutritional research; nevertheless, understanding of these is surprisingly limited.  According to Gordon (1959) one of the most striking features of insect nutrition research is the difficulty in producing characteristic effects as observed in mammals, because a deficiency in any essential nutrient in insects usually causes merely cessation of growth and prolonged survival.

….the term “nutritional diseases” refers to abnormalities caused by the absence, insufficiency, or excess of one or more nutrients; a “symptom” is any perceptible change in the body or its function that indicates disease.  The term “gross pathology” refers to obvious conditions, such as paralysis, abnormal coloring, and morphological abnormalities; the term “physio-chemical” refers to abnormalities not visible to the naked eye, such as changes in pH, osmotic pressure, or chemical composition; the term “histopathological” refers to abnormalities in the tissues, cells and other microstructures that are detectable only by histological or histochemical factors essential to the adequacy of the ingested food.  The term “imbalance” means a relative deficiency of an essential nutrient that results from an immoderate excess of one or more other nutrients.

In general, insects require for growth the common ten essential amino acids, six or more B vitamins, a sterol such as cholesterol, and a number of inorganic salts; some species require carbohydrates, certain fatty acids, and components of nucleic acids; and a few may need miscellaneous and unidentified substances…..moreover, the presence of certain substances may determine the need for another.”

In contrast to these requirements for larval insects, some adult insects do not feed at all, and others have more limited needs than the immature forms.

“Quantitative requirements for some substances depend on a number of factors; for example, vitamin and energy requirements depend on metabolic rate, and in some cases on the dietary protein level.

….In some species intestinal microflora or intracellular symbiotes supply nutrients, particularly vitamins….when these microorganisms were eliminated, the nutritional requirements of the insect concerned were found to be quite ordinary.”

“The usual assumption is that a dietary component is an essential nutrient if its omission results in poor growth, though if the component in question is a phagostimulant, poor growth may be caused by a reduction in feeding activity.”

“Gordon (1959) reasoned that in insects cessation of growth resulting from a deficiency of any essential nutrient is probably a mechanism for efficient survival under highly unfavorable conditions, as it avoids the wasteful and lethal biochemical imbalances that mammals create when they continue to grow on deficient diets.  Slow or arrested growth and development, diminutive size, and high or complete mortality of the immature stages, and little or no reproduction in the adult, are familiar symptoms of most nutritional defects.”

“When newly emerged honey bees, Apis mellifera Linnaeus, were fed on pure sugar, but without pollen, the bees lacked vitality, remained motionless on the comb, and mortality was high (Haydak, 1937).  These effects were probably caused by lack of protein, though the possibility of deficiencies of vitamins and other substances must be considered. ….On protein-deficient diets, A. mellifera became paralyzed, chitin became brittle, hair was lost, and the wings broke off—especially in nurse bees—as nitrogenous reserves were depleted, mostly from the integument, when the hive was depleted of pollen for a long time (Butler, 1942). “

“Symptoms of carbohydrate deficiency in the adult female of some species are retardation of ovarian development and decreased or no egg production….Possibly such conditions may arise in many insects in natural environments under special circumstances; for example, dietary carbohydrates are needed for normal reproduction in the female mosquito….only at suboptimal temperatures (Hecht, 1933).”

“Although an insect may develop from egg to adult on a food at near normal rate, it may show obvious symptoms of malnutrition when it attempts to reproduce or is reared on the same diet through the second or third generation.  Growth of Agria affinis on chemically defined diets was exceptionally good, judged by developmental rate and larval size finally attained (House and Barlow, 1960), but histological examination (Dr. Joan F. Bronskill, unpublished) of individuals reared on the best diets showed that the fat cells, midgut epithelium, and muscular tissues had a “starvation-like” appearance, and that the embryonic development of eggs in almost all mated females was arrested in the blastular stage.  Thus starvation may occur on diets seemingly adequate for larval development if qualitative or quantitative deficiencies are sufficient to partially starve certain metabolic processes.   In nature malnutrition in insects results from shortages of food and from variations in the composition of foodstuffs.  Undoubtedly this plays an important role in insect control, though it is difficult to make an evaluation of it.  Seamans (1938) described how starvation can control the cutworm Agrotis orthogonia when the soil is cultivated and kept free of all plant growth for a period in the spring.  Examples may be found where other nutritional defects possibly were involved in pest control, such as in varietal resistance of peas to the pea aphid Acyrthosiphon pisson (Harris).  ….Gordon (1959) pointed out that a diet optimal in the early period of growth may be suboptimal in the later period, and vice versa.  ….The nutrition of host plants may be influenced by application of fertilizers and nutritional sprays, by insecticidal and fungicidal sprays, and by soil insecticides; consequently phytophagous insects are affected in various ways (Rodriguez, 1960).

…..many workers showed that that susceptibility to insecticides was affected by the kind and quantity of food eaten by insects or stored in their body tissues (Gaines and Mistric, 1960).  …  Bergold (1958) concluded that the quality and kind of food seem to play a very important part in the susceptibility of an insect population to virus diseases.

….comparative data may be needed on the effects of physical factors, and especially of toxins and poisons, on insect tissues.  For example the effects of DDT and of starvation on Popillia japonica were characterized by only slight differences (Ludwig and Bartolotta, 1953; Ludwig and Cullen, 1956).

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"Oh what a tangled web we weave when first we practice...."  This information about nutrition in insects was known back in the 1950's.  So, what is the state of insect nutritional research today?  It seems that nothing of substance has happened.  If you Google Scholar "Insect nutrition" this reference is the first one to come up.  Conclusion:  we don't know much.

Christina


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