Fanessay分享一篇essay范文--The insect life cycles，本篇文章讨论的内容是关于昆虫的生命周期。昆虫的生命周期一般是根据昆虫的变态程度分为代谢型、半代谢型与完全变态型。代谢是指发育过程中无明显变化的昆虫，具有这种特征的昆虫通常是进行书上地位比较低的昆虫。半代谢型指昆虫的生命周期分为三个阶段：卵、若虫与成虫。和无代谢相比，就有更多可识别的特征。第三种，是最先进的一种完全变态，经历了卵、幼虫、蛹与成虫4个阶段，包括更先进的物种在翼龙。和半代谢比较，完全代谢给昆虫带来了更大的灵活性。
This essay briefly introduces the 3 types of insect life cycles as well as discusses about Colony Collapse Disorder (CCD) and its effects and social importance in basic and applied science.
The life cycles of insects are commonly divided in 3 types, according to the extent of their metamorphosis in their life spans, namely ametabolism, hemimetabolism and holometabolism. Ametabolism refers to those insects without obvious changes during their development processes. Insects with this feature are usually those lower ones in the evolutionary tree, such as apterygota. Hemimetabolism refers to insects with 3 phases in their life cycle: egg, nymph and adult. It has more recognisable features comparing to the ametabolism. The third one, also the most advanced type is holometabolism, insects of which experience 4 phases: egg, larva, pupa and adult. It includes more advanced species in Pterygota.(Danks, 1994).
In general, the main difference between hemimetabolism and holometabolism is the existence of pupa, which can be seen as a transition from larva to adult. During this phase, the larva would completely stop feeding, with destruction of some of the larva structures and formation of the adult structures. It is a relatively weak phase, as most pupas cannot react to the environment. As a result, they appear in seasons with fewer predators and generate hardened carapaces to protect them from harsh outside environment (Danks, 1994). From this point of view, insects of holometabolism are more flexible and better developed comparing to those of hemimetabolism.
Colony Collapse Disorder (CCD) is a term originally used to describe a mysterious phenomenon happed in honey bee (Apis mellifera L.) colonies. In recent decades, in wild and breeding honey bee colonies, most bees, especially worker bees, would suddenly disappear from their hives, abandoning all the work of feeding larva and taking care of the queen bees without any apparent reason. No evidence showed that they have experienced life-threatening danger or lack of food (Lu et al., 2012). Researchers has put forward a range of hypothesis, such as pesticides effects, unexpected parasite or pathogen infection and stress that hit worker bees and weaken the whole colony (Johnson, 2010). However, there has not been a certain factor that was found to be the main reason of all cases.
The effect of CCD to a bee colony is obvious devastating, let alone to the whole population. The tremendous deduction of honey bees can lead to a large decrease of plant population, which might cause disaster like famine. So far it has brought a huge strike to the beekeeping industry, which caused numerous financial losses (Lu et al., 2012).
In summary, holometabolism brings more flexibility to insects than hemimetabolism. As for the CCD, a solution is required to stop it, otherwise it may lead to dramatic natural and societal disaster.
Danks, H. V. (1994). Insect life-cycle polymorphism: theory, evolution and ecological consequences for seasonality and diapause control.. Insect life-cycle polymorphism : theory, evolution and ecological consequences for seasonality and diapause control. Kluwer Academic.
Lu, C. S., Warchol, K. M., & Callahan, R. A. (2012). In situ replication of honey bee colony collapse disorder. Bulletin of Insectology, 65(1), 99-106.
Johnson, R. (2010). Honey bee colony collapse disorder.