tailieunhanh - Entomology 3rd edition - C.Gillott - Chapter 23

23 The Biotic Environment 1. Introduction This chapter will deal with the biotic environment of insects, which is composed of all other organisms that affect insects’ ability to survive and multiply. In other words, the interactions of insects with other organisms will be discussed. | 23 The Biotic Environment 1. Introduction This chapter will deal with the biotic environment of insects which is composed of all other organisms that affect insects ability to survive and multiply. In other words the interactions of insects with other organisms of the same and other species will be discussed. Food is the most obvious and important biotic factor and insects are involved in a wide spectrum of trophic relationships with other organisms both living and dead. As the majority of insects feed on plant material in one form or another they are key components in the flow of energy through the ecosystem. However other interactions are known that though not as easily recognized as feeding are nonetheless important regulators of insect distribution and abundance. 2. Food and Trophic Relationships Insects have evolved diverse feeding habits that allow them to exploit virtually every naturally occurring organic substance. Among their adaptations are specialized ingestive and digestive systems the ability to detoxify or physically avoid toxins produced by the host mutualistic relationships between the insect and microorganisms and life-history strategies that result in temporal avoidance of resource-poor situations including those resulting from interspecific competition or times when the host s toxins are abundant. Thus insects participate in an array of trophic interactions as herbivores predators parasites parasitoids detritivores and prey in both terrestrial and freshwater ecosystems Figures and . Food may be an important limiter of insect population growth it may also affect the distribution and the dispersal of species over time Price 1997 . . Quantitative Aspects Though the amount of food available might be considered as an important regulator of insect abundance it has been found in natural communities that populations do not normally use more than a small fraction of the total available food. This is primarily because other 691 692 CHAPTER 23