Food preferences, insects

Toxic substances acquired from the host plaint may provide resistance to parasitoids (24), pathogens (25), and predators (45). By avoiding some toxins in plant material and selecting superior food tissues, insects feeding on variable hosts may become more susceptible to some enemies. Of course, other substances in preferred tissues may still be toxic to certain of these enemies, but this is less likely than it would be were plant compounds uniformly encountered by the host insect. 

Ryuda, M., Tsuzuki, S., Tanimura, T., Tojo, S. and Hayakama, Y. (2008). A gene involved in the food preferences of larval Drosophila melanogaster. J. Insect Physiol., 54, 1440-1445. 

To investigate food preferences by insects or other herbivores, such as deer (Rautio et al. 2008), and the compounds responsible for their choices, these compounds can be added to their diet and tested in feeding bioassays. Here we will add a mixture of phenolic compounds, known as tannic acid, to the diet of homworm caterpillars. The tobacco homworm, Manduca sexta, normally feeds on Solanaceae such as tomato or potato plants. For more on the natural history of this insect, consult the information sheet prepared by the biological supply company that ships these caterpillars. 

Use the pest-control strategies in this section to lure pests into situations from which they can t escape. Pest baits and lures can be visual (using color or light to attract the pest), sexual (using pest-specific pheromones), or dietary (using preferred insect foods or kairomes, which are feeding stimulants). 

Consistent with the drastic change in food preference after metamorphosis, the expression pattern of ORs in the adult insect olfactory organ differs from that in the larval olfactory organ and also shows sexual dimorphism. In Drosophila, the adult expresses 40 ORs, 30 of which are expressed in antennae. Larvae express 25 ORs (Fishilevich et al. 2005 Kreher et al. 2005), 14 of which are larva-specific. As described below, a subset of adult-specific ORs responds to food odors, whereas ten of the 30 adult-specific ORs are specifically expressed in trichoid sensilla and are strongly inhibited or only weakly activated by food-related odors, consistent with then-purported role in pheromone rather than food detection. ORs expressed specifically at each developmental stage are likely to be essential for survival during the stage. 

Jermy, T. (1966) Feeding inhibitors and food preference in chewing phytophagous insects. Ent. exp. appL, 9, 1-12. 

Highly toxic substances, such as cyanides, are sometimes feeding cues and stimulants for specialized insects. For example, instar larvae of the southern armyworm (Spodoptera eridania) strongly prefer cyanogenic foods, such as foliage of the lima bean, a plant with comparatively elevated cyanide content — up to 31 mg/kg in some varieties — in the form of linamurin (Brattsten et al. 1983). Feeding was stimulated in southern army worms at dietary levels up to 508 mg KCN/kg... 

Sinigrin (III), a glycoside produced by many species of cruciferous plants, can be converted to a highly toxic aglycone, allylisothiocyanate (IV), after hydrolysis by adapted and nonadapted Insects ( 5, 1, lA). On the other hand, the mustard oil is the preferred storage form of larvae of two Pieris species, brassicae and rapae, which had developed on food... 

About 85% of all Insects are holometabolous, and the food plants of larval and adult stages often differ (28). In most holometabolous insects host recognition may have been predetermined for the larva by the ovipositing female ]). In some cases it has been demonstrated that the larva prefers to eat the food upon which they are initially fed (Induction), even if it s not the appropriate host (29). 

A number of resistance factors influence behavioral processes and hence determine an insect s preference or non-preference for a particular plant. Hosts which do not contain the proper kairo-monal compounds are often totally rejected as food plants and by ovipositing females. Dethier (29) noted, however, that plants are almost never neutral, but are aTmost always either attractive or repellant. As previously observed, the ovipositional choice of the female imago and the food choice of the larvae usually coincide ( ). 

Wackers, F. L. (1994). The effect of food-deprivation on the innate visual and olfactory preferences in the parasitoid Cotesia rubecula. Journal of Insect Physiology 40 641-649. 

Insect preferences for certain types of food can be considered from a chemical ecological point of view as follows presence of attractant, fixing factor oviposition-stimulant, and feeding stimulant absence of repellent, oviposition deterrent, feeding deterrent, nutritional defect, and growth-deterrent. Conversely, the opposite is true for certain food types undisturbed by insects. 

The same conclusions were also recorded for vertebrate herbivores. For example rabbits (Cuniculus europaeus) and hares (Lepus europaeus) clearly prefer the sweet plants and leave the bitter plants almost untouched, at least as long as there is an alternative food source. In conclusion, although taste perception in mammals and insects differs in many aspects, there also some similarities both in anatomy and in the function of the bitter taste perception. A comparison of the effects of alkaloids, as well as of other bitter compounds, will be assisted by further advances in the knowledge of the structure of taste genes and receptors. 

On the other hand, microorganisms and herbivores rely on plants as a food source. Since both have survived, there must be mechanisms of adaptations toward the defensive chemistry of plants. Many herbivores have evolved strategies to avoid the extremely toxic plants and prefer the less toxic ones. In addition, many herbivores have potent mechanisms to detoxify xenobiotics, which allows the exploitation of at least the less toxic plants. In insects, many specialists evolved that are adapted to the defense chemicals of their host plant, in that they accumulate these compounds and exploit them for their own defense. Alkaloids obviously function as defense molecules against insect predators in the examples studied, and this is further support for the hypothesis that the same compound also serves for chemical defense in the host plant. 

NABID BUGS (nabidae). These are very big and can even overcome leafrol-ler caterpillars. A characteristic feature of this type of bug is the curved rostrum, which is kept close to the body when not being used. Their preferred food is aphids and other small insects. 

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