Insect parasitoids

The nematodes are themselves insect parasitoids that are not very particular about their hosts. Fly maggots, moth larvae and pupae, beetle larvae, and numerous other hosts are all acceptable to them. Some of these nematodes do have narrow preferences, but one widespread species invades more than two hundred different kinds of insects. Juvenile nematodes infected with their bacteria seek out a host to parasitize, typically gaining entry through one of its body orifices. Some species enter through a hole they scrape in the insect s cuticle using a "tooth" on their head. Once inside the insect, the worms force their way through soft tissues and into their host s central body cavity. 

Tumlinson, J. H., Turlings, T. C. J. and Lewis, W. J. (1992). The semiochemical complexes that mediate insect parasitoid foraging. Agricultural Zoological Review 5 221-252. 

In many cases, the volatile compounds emitted from leaves as a result of insect damage allow insect parasitoids and predators to distinguish between infested and uninfested plants, and therefore help to locate hosts or prey [230]. In the majority of plants reported so far, there are remarkable similarities in the structure of VOCs that are emitted from insect-damaged leaves [231]. This structural uniformity suggests the activation of a common set of biosynthetic pathways shared by a wide range of plants, and that the products are detectable by a broad spectrum of insect parasitoids and predators. For instance, nicotine is one of the most broadly effective plant defence metabolites known because it poisons acetylcholine receptors and is thus toxic to most heterotrophic organisms with neuromuscular junctions. 

Relatively little is known of the physiology and metabolism of insect parasitoids. Though it is generally assumed that the maturing parasitic hymenopteran eggs take up host hemolymph components and ions through its thin wall (17. 25) it has been shown that some parasitoids rely on their protein synthetic machinery for growth (25. 26). Much of this synthesis occurs after the parasitoid is associated with the host (27). 

Because 2-tridecanone-mediated resistance to sexta and L. decemlineata is genetically distinct from the lamellar-based resistance to zea, it would be possible to develop tomato cultivate resistant to sexta and decemlineata but susceptible to zea. On such cultivate, the 2-tridecanone-mediated induction of elevated tolerance to some insecticides might make control of zea more difficult (55, 58). The severity of H. zea as a pest problem on such cultivate would be further exacerbated if 2-tridecanone associated with the resistant foliage seriously interfered with insect parasitoids and predators important in suppressing natural populations of zea. Because of its occurrence in the foliar glandular trichomes, and because of its broad spectrum toxicity to insects, we considered it likely that parasitoids and predaceous insects searching the resistant foliage for prey would be exposed to potentially toxic levels of 2-tridecanone. 

Duffey, S. S., K. A. Bloem and B. C. Campbell. 1986. Consequences of sequestration of plant natural products in olant-insect-parasitoid interactions, pp. 31-60. In D. J. Boethel and R, D. Eikenbary (eds,). Interactions of Plant Resistance and Parasitoids and Predators of Insects. Ellis Horword Ltd., Chichester. 

Dahlman, D. L. and Vinson, S. B. (1977) Effect of calyx fluid from an insect parasitoid on host hemolymph dry weight and trehalose content. J. Invert. Path., 29, 227-9. 

Fisher, R. C. (1963) Oxygen requirements and the physiological suppression of supernumerary insect parasitoids. J. exp. Biol, 40, 531-40. 

Fisher, R. C. and Ganesalingam, V. K. (1970) Changes in the composition of host haemolymph after attack by an insect parasitoid. Nature, 227, 191-2. 

Guillot, F. S. and Vinson, S. B. (1972) Sources of substances which elicit a behavioral response from the insect parasitoid, Campoletis perdistinctus. Nature, 235, 169-70. 

Salt, G. (1968) The resistance of insect parasitoids to the defense reactions of their hosts, Biol. Rev. Camb. Phil., 43, 200-32. 

Vinson, S. B. and Guillot, F. S. (1972) Host-marking source of a substance that results in host discrimination in insect parasitoids. Entomophaga, 17, 241-5. 

Smith, D. A. S. (1978a) Cardiac glycosides in Danaus chrysippus (L.) provide some protection against an insect parasitoid. Experientia, 34, 844-5. 

Salt, G. (1961) Competition among insect parasitoids. In Mechanisms in Biological Competition. Symp. Soc. exp. Biol., 15, 96-119. 

Barbieri RL, York CM, Cherry ML, Ryan KJ (1987) The effects of nicotine, cotinine and anabasine on rat adrenal 11 [3-hydroxylase and 21-hydroxylase. J Steroid Biochem 28 25-28 Barbieri RL, Eriedman Al, Osathanondh R (1989) Cotinine and nicotine inhibit human fetal adrenal 11 3-hydroxylase. 1 Clin Endocrin Metabol 69 1221-1224 Barbosa P, Saunders JA, Kemper J, Trumbule R, Olechno J, Maitinat P (1986) Plant aUelochemicals and insect parasitoids. Effects of nicotine on Cotesia congregata Say (Hymenoptera Braconidae) and Hyposoter annulipes Cresson (Hymenoptera Ichneumonidae). J Chem Ecol 12 1319-1328... 

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