Search

Before the establishment of an insect can take place, a complicated set of circumstances and conditions usually must exist (Smith et al., 1933). As pointed out by Elton (1927) in his discussion of the dispersal of animals, “…only a tiny fraction of the original emigrants will ever succeed in establishing itself even temporarily…”

In reviewing the literature dealing with biotic potential it is found that there are two conceptions as to the importance of this general idea. Brues, considering it in the light of ultimate insect abundance, concludes that it is relatively unimportant and that environmental resistance plays the great part in the fluctuation and stabilization of insect populations. Many illustrations can be given showing that this view is fundamentally correct when time is not considered as a factor. Chapman and his students consider that time is of definite importance and therefore give to biotic potential a place of much greater value.

The presence of insects in unusual numbers is generally recognized as being due to the decrease in environmental resistance, thus permitting the reproductive ability or “Biotic Potential” of the insect to assert itself, at least in part. Environmental resistance as defined by Chapman includes such factors as parasitism and lack of food, also all of the factors usually classified under physical autecology unless these are operating at their optimum.