I examined the effect of heterogeneity in the thermal environment on the life history of the cricket Allonemobius fasciatus. Variation in the life cycle was the result of a mixture of phenotypic plasticity and genetic differentiation in phenology-related traits along a latitudinal cline in growing season. Females from a partially bivoltine population have a conditional life history because they can adjust the proportion of diapause eggs in accordance with the likelihood that a second generation will grow and reproduce before winter. The thermal environment is not variable enough to result in the evolution of a marked bet hedging response, as is predicted by theory. A quantitative genetic analysis of the diapause reaction norm revealed significant heritabilities as well as correlations with other traits that could be related to common physiological mechanisms.

The influence of photoperiod and genotype on thermal preference of juvenile Gryllus firmus was explored. Both rearing condition and genotype affect temperature preference. The following results were obtained: (1) the wing morph of juveniles raised at 28$ sp circ$C 16hL:8hD is determined before 20 days post hatching. (2) Crickets distribute themselves on the apparatus differently in the presence of a thermal gradient than in its absence: such controls for positioning preference are rare in the literature. (3) Juveniles younger than 20 days old tend to choose higher surface temperatures and achieve higher body temperatures if either rearing photoperiod or selection predisposes them to microptery and choose lower temperatures if they are predisposed towards macroptery. (4) The differences in thermal preference between presumptive macropters and micropters remains significant after differences in body size are taken into account. The differences in thermal preference could act as a novel mechanism for lowering the heritability of wing morph.

Please read the abstract in the 00front part of this document / Dissertation (MSc (Zoology))--University of Pretoria, 2006. / Zoology and Entomology / unrestricted

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2 pp. / Indian house crickets and field crickets are the two most common crickets in Arizona. Although these crickets do not bite or carry diseases, they are considered a nuisance because of their "chirping". This publication focuses on common crickets found in Arizona, including the Indian house crickets, field crickets, and Jerusalem crickets. It also discusses the problems they cause and the strategies to control them.

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The house cricket, Acheta domesticus (L.), is an insect which has received, up until recently, very little attention as a physiological subject. This is no doubt due to the fact that it has been of little economic importance in Europe or North America. However, its potential as a laboratory test animal has been pointed out by several authors (Stone, 1953; Ghouri and McFarlane, 1958; Ritchot, 1960 ). Several factors enhance its utility - it is easily reared; it is a large enough insect in all stages of its life history to require no special handling, techniques; it has a sufficiently short life history; and finally it is not commonly subject to diseases or parasites in the laboratory.

In captivity the diversity of prey items for obligate insectivores is limited and nutritionally inadequate, leading to nutrient deficiencies. Zoological institutions utilize gut-loading, an insect supplementation technique, to compensate for these nutrient shortcomings. This study developed a gut-loading diet (GLD) to enhance the nutritive quality of the domestic house cricket (Acheta domestica) for insectivorous amphibians and reptiles, with the requisite that it also met cricket foraging and palatability needs. Gut-loaded cricket analysis established its effectiveness such that the targeted level of most nutrients required by the end consumers were met after consuming the diet for 24 hrs (Ca:P of 1.127; vitamin A (retinyl acetate) level of 12,607 IU/kg; vitamin E level of 342 IU/kg and a linoleic fatty acid level of 4.62%), peaking at 2 days for some and remained above targeted amounts for at least 4 days. A list of cricket gut-loading optimization husbandry procedures has also been recommended.

Falconer (1989) made the statement that traits closely related to fitness generally experience greater inbreeding depression than traits less closely related to fitness. However, he did not provide statistical support for this statement. In a review of the literature I provide statistical support for Falconer's (1989) statement by showing that life history traits (closely related to fitness) display more severe inbreeding depression than morphological traits (less closely related to fitness). Because inbreeding depression is greater in traits closely related to fitness, it may impact the success of colonization. In an investigation of the influence of inbreeding in a colonizing wing dimorphic species of cricket, Gryllus firmus, I have provided further empirical support for Falconer's (1989) statement, in addition to showing that inbreeding does not affect the equilibrium morph frequencies between two the morphs of G. firmus.