Regulation of hemolymph and whole-body Mg ++ concentration was studied in the larvae of Aedes campestris Dyar and Knab from a salt-lake containing 190 m Eq Mg++/litre. Hemolymph Mg++ concentration of the larvae responded quickly to a change in external Mg++ concentration and reached a new level after one day. Over a wide range (0.02 to 200 m Eq/litre) of external Mg++ concentrations the blood Mg++ concentration changed only from 4 to 8 m Eq/litre. The rate of entry of Mg++ into the larvae by drinking was 19 to 57 n Eq/mg x hr. Drinking rate was found to be independent of temperature (10C- 22C), Mg++ concentration (100- 300 m Eq/litre), and presence of particles in the medium. More than 95% of the ingested Mg++ was absorbed from the midgut. Whole-body Mg++ content of larvae remained low, indicating that excess Mg++ was not stored in tissue. Measurement of urine Mg++ concentrations of animals in different media showed that excretion via urine could account for all of the ingested Mg++. Anal papillae need not therefore be implicated in Mg++ excretion in Aedes campestris larvae. / Science, Faculty of / Zoology, Department of / Graduate

Call number: LD2668 .T4 1957 B57 / Master of Science

Call number: LD2668 .T4 1959 S67

Call number: LD2668 .T4 1986 S56 / Master of Science / Entomology

The development of immature insects is commonly employed in forensic investigations to estimate time of death, or postmortem interval (PMI), of a corpse on which they are feeding. The bulk of this thesis focuses on factors influencing the accuracy of developmental data, and exploring how and why developmental data differ between studies involving the same species, and between different species. Because carrion feeding insects are ectotherms, temperature may be expected to significantly influence their behaviour, development and distribution, and the remainder of the thesis therefore focuses on the thermal biology and geographical distribution of seven forensically important blowflies. The species include Chrysomya albiceps, C. putoria, C. chloropyga, C. megacephala, C. marginalis, C. inclinata and Calliphora croceipalpis. A robust experimental design for estimating developmental models is outlined and tested. It is recommended that forensic entomologists should involve at least six constant temperatures, starting at about 7°C above the relevant developmental zero (D0) and going to about 10°C above the upper critical temperature, and a temporal sampling interval with a relative precision of about 10%. Using this design, focused experiments consistently provided the most reliable developmental data, while data pooled from different studies yielded inconsistent results. Similarly, developmental data from closely related species differed significantly, and surprisingly so did developmental data from different populations of the same species. Possible explanations for the latter lay in the different methods of data collection but only temporal sampling resolution had a direct influence on the accuracy of developmental data. Consequently, disparities in such data were primarily ascribed to genetic differences and phenotypic plasticity. Comparisons between numerous thermal thresholds of larvae, pupae and adults support this conclusion and suggest a phylogenetic component to the thermal biology of blowflies. Further comparisons were made between these temperature thresholds and the distributions of blowfly species present on two rhinoceros carcasses. These comparisons suggest that blowfly larvae with high upper lethal temperature thresholds dominate in interspecific competition in favorable thermal environments by raising maggot mass temperature above the thresholds of other carrion-feeding blowflies, through maggot-generated heat. Bioclimatic modeling using maximum entropy analysis provided a successful means of predicting whether a species is likely to occur in an area, and whether it would therefore be expected in a local carcass community. It also showed that temperature was less important than moisture in shaping the geographical distribution of African carrion blowflies. Based on these results, several recommendations are made for the practice of forensic entomology.