University of Adelaide

About: University of Adelaide is a education organization based out in Adelaide, South Australia, Australia. It is known for research contribution in the topics: Population & Pregnancy. The organization has 27251 authors who have published 79167 publications receiving 2671128 citations. The organization is also known as: The University of Adelaide & Adelaide University.

Diapause in relation to the ecology of insects

Abstract: Diapause is an important adaptation in insects which recurs in many species enabling them to persist in regions which would otherwise be unfavourable for permanent habitation, and to maintain high numbers in an environment which might otherwise support only a low population. Frequently diapause occurs in that stage of the life cycle which is highly adapted to resist the rigours of the climate. Thus in the grasshopper Austroicetes diapause occurs in the egg stage, which by virtue of an incredibly effective mechanism for preventing evaporation and at the same time allowing the absorption of water as opportunity offers is able to withstand great extremes of desiccation and thus survive the arid summer (Birch & Andrewartha, 1942, 1944). More commonly in species adapted to the cool temperate zones of the Northern Hemisphere diapause occurs in a stage in the life cycle which is able to withstand extremes of cold. Or diapause may be of value to the species because it induces a rhythm in the life cycle which synchronizes with the rhythm of the environment and ensures that the active stages of the life cycle shall be present when there is an abundance of food and the other components of the environment favour rapid development and high survival. Throughout this article, species have been referred to by generic names except where this would be ambiguous; then the specific name has been given. In order that the references may be followed more readily all the species mentioned in the text have been brought together in Table I in alphabetical order of generic names

Melanism and disease resistance in insects

Abstract: There is growing evidence that insects in high-density populations invest relatively more in pathogen resistance than those in low-density populations (i.e. density-dependent prophylaxis). Such increases in resistance are often accompanied by cuticular melanism, which is characteristic of the high-density form of many phase polyphenic insects. Both melanism and pathogen resistance involve the prophenoloxidase enzyme system. In this paper the link between resistance, melanism and phenoloxidase activity is examined in Spodoptera larvae. In S. exempta, cuticular melanism was positively correlated with phenoloxidase activity in the cuticle, haemolymph and midgut. Melanic S. exempta larvae were found to melanize a greater proportion of eggs of the ectoparasitoid Euplectrus laphygmae than non-melanic larvae, and melanic S. littoralis were more resistant to the entomopathogenic fungus Beauveria bassiana (in S. exempta the association between melanism and fungal resistance was non-signficant). These results strengthen the link between melanism and disease resistance and implicate the involvement of phenoloxidase.