Effects Of Nutrition On Individual Growth

Individual growth of immature insects is strongly influenced by food availability, feeding selectivity, and food quality. Insect growth is often directly related to food availability, in that larval growth rates are highest in the presence of an abundant food supply. Because availability of food resources can vary temporally, growth responses also can be expected to vary throughout the year. For example, several species of stream chironomids (Diptera: Chironomidae) that feed primarily, but not exclusively, on attached algae, exhibit periods of maximal larval growth that coincide with times of the year when instream algal production is highest.

Feeding selectivity and food quality, however, also influence the relationship between growth and food availability. Even in the presence of an apparently abundant food supply, larval growth rates may be reduced if that food resource is not preferred or if it is of low quality or lacking essential nutrients. For example, the leaf-shredding crane fly, Tipula abdominalis, shows a strong preference for hickory, maple, and American chestnut leaves and a low preference for American beech, white oak, and red oak leaves. Larval growth rates are highest on the more preferred leaf types and lowest on the less preferred leaves. The higher growth rates on more preferred leaves are not due to higher food conversion efficiencies, but rather result from increased consumption rates due to a more palatable food source.

Although food availability may not be a limiting factor for growth in some insects, food quality may impose a substantial constraint to larval growth. Differences in food quality also can affect larval growth rates and the ability to complete development and reproduce. Absolute and relative growth rates of the caddisfly Clistoronia magnifica (Trichoptera: Limnephilidae) reared on diets differing in quality were significantly higher on a diet rich in triglycerides (conditioned alder leaves plus whole wheat grains) compared with diets of conditioned alder leaves, conditioned alder leaves with a fatty acid mixture, conditioned alder leaves plus hyphomycete fungi, or hyphomycete fungi alone. In addition, only larvae fed the high-triglyceride diet successfully completed development and reproduced. Some insects, however, even in the absence of higher quality food, can maintain a relatively uniform growth rate throughout development by increasing ingestion rates of lower quality food.

See Also the Following Articles

Body Size • Development, Hormonal Control of • Exoskeleton • Feeding Behavior • Nutrition • Temperature, Effects on Development and Growth

Further Reading

Berg, M. B., and Hellenthal, R. A. (1992). Life histories and growth of lotic chironomids (Diptera: Chironomidae). Ann. Entomol. Soc. Am. 85, 578-589.

Chapman, R. F. (1998). "The Insects: Structure and Function." Cambridge University Press, Cambridge, U.K.

Crosby, T. K. (1972). Dyar's rule predated by Brook's rule. N. Z. Entomol. 5, 175-176.

Dyar, H. G. (1890). The number of molts of lepidopterous larvae. Psyche 5, 420-422.

Epstein, M. E., and Henson, P. M. (1992). Digging for Dyar. Am. Entomol. 34, 148-169.

Gillott, C. (1980). "Entomology." Plenum Press, New York. Richards, O. W., and Davies, R. G. (1979). "Structure, Physiology, and Development," Vol. I of "Imm's General Textbook of Entomology." Chapman & Hall, London. Sweeney, B. W. (1984). Factors influencing life-history patterns of aquatic insects. In "The Ecology of Aquatic Insects" (V. H. Resh and D. M. Rosenberg, eds.), pp. 56-100. Praeger, New York. Ward, G. M., and Cummins, K. W. (1978). Life history and growth pattern of Paratendipes albimanus in a Michigan headwater stream. Ann. Entomol. Soc. Am. 71, 272-284. Wigglesworth, V. B. (1965). "The Principles of Insect Physiology." Methuen, London.

(Rock Crawlers, Ice Crawlers)

California Academy of Sciences

The Grylloblattodea, or ice crawlers, are a small group of soft-bodied, apterous, terrestrial and termitelike insects confined to the Northern Hemisphere. They occur under rocks in forest leaf litter or above the treeline in the high mountains. In parts of the United States, Canada, and China they are found under rocks in soil at or below freezing temperature. In Japan and Korea, they are active in midsummer in the deep leaf litter of mixed conifer and deciduous forests, where daily ambient temperatures approach 30°C. In Japan and Korea some have been found in caves; in the western United States, they are known from subterranean lava tubes. Grylloblattids are slender, depressed insects covered with fine hairs and having reduced eyes. Adults range from 2 to 3.5 cm in length. Ice crawlers appear to be primarily nocturnal. They are considered to be some of the most primitive of orthopteroid insects and have been thought to be related to cockroaches (Blattodea) and stick insects (Phasmida).

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