Deterrents, terpenes

Table IV gives a few examples of terpenes shown to be Insect deterrents. As with the previous examples of Insect attractants In Tables II and III, the structural diversity of the deterrent compounds Is remarkable. There are no clear and logical structure-activity relationships among the compounds with these behavioral effects. Specialised and unique effects and behavioral adaptations are thus the rule In Interactions between species rather than the exception.

Soft corals eggs contain terpenes such as 116, 117, and epoxypukalide 118 that are believed to play a defensive role.146,147 Extracts of Sinularia polydactyla larvae containing 116 and 117 are deterrent in assays with C. solandri which has been observed feeding on soft coral polyps in the field.147... 

Dioryctria abietivorella oviposits on white pine in response to volatile emissions of myrcene and 3-carene (11.36).166 Terpenes can both deter and stimulate oviposi-tion of the European corn borer. In a series that was screened, the best deterrent was farnesal and the best stimulant a-humulene (11.37).167... 

Ironically, terpenes serve both as major deterrents to feeding and as attractants for animals (Hedin et al., 1974). Volatile compounds are often involved in long-distance interactions and are especially important as attractants and repellents (Kogan, 1975). 

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