The flight activity of three species of Simuliidae was studied in the Eden Valley, Cumberland. The flies were caught using a net mounted on a vehicle, which was driven at 48 km/h along a circuit, consisting of four roads parallel to the River Eden (at distances of 0.5, 1.5, 5.0 and 6.0 km from the river), and the main road at right angles to the river, between the villages of Langwathby and Melmerby. Equipment in the back of the vehicle allowed the flow of insects from the net to be divided into catches, each of which was caught over a distance of 1 km. An anemometer on the mouth of the net allowed the insects to be calculated as a concentration, so that the catches on the four roads could be directly compared. The female flies were all dissected and thus divided into different physiological groups. The main divisions were into nulliparous and parous flies, each of which was sub-divided into blood-thirsty and blood-fed flies, and into gravid and parasitised flies. The diurnal rhythm of the three simuliid species was studied, noting the differences between the different physiological groups. The effect of the weather on these rhythms was examined. By comparing the four parallel roads, the spatial distribution of the three species was studied. The distribution, and thus powers of dispersal, of the nulliparous and parous flies was compared, and the effect of the presence of parasites on this ability to disperse was noted.

Stalk-eyed flies are characterised by having eyes that project laterally from the head. Male eyespan is known to be subject to sexual selection via female mate preference for exaggerated ornaments. This thesis examines reproductive quality and mating strategy in both sexes, in laboratory and field populations, using two species that are sexually dimorphic for eyespan. Using the African stalk-eyed fly species Diasemopsis meigenii I examined male sperm allocation during single and multiple matings. I demonstrate that during single matings males allocate larger quantities of sperm to highly fecund females. However, large eyespan males do not transfer more sperm than small eyespan males, despite having larger reproductive organs. All males are subject to ejaculate depletion during multiple matings, but small eyespan, and thus unattractive, males suffer the greatest degree of depletion. I conducted novel field observations of the Malaysian stalk-eyed fly Teleopsis dalmanni to examine female sperm limitation and direct benefits of mating. Highly fertile females do not benefit from an additional mating, while less fertile females can dramatically increase their fertility with the sperm from a single mating. Sperm limited females show increased receptivity to additional matings by engaging in a first copulation sooner than recently mated females. Female fecundity was positively correlated with sperm storage, suggesting that the presence of sperm in the reproductive tract acts as a trigger for egg maturation. Finally, I asked whether male and female eyespan, and the different reproductive strategies believed to be associated with the eyespan trait, resulted in differences to the trade-off between reproduction and soma. Using dietary manipulation I show that both males and females incur a cost of reproduction, as reproductive traits show reduced size under harsh conditions. Using extractable lipid content as a measure of somatic investment, I show that both males and females retain fewer lipids in their soma under harsh dietary conditions. But I find very little evidence for varying reproductive and somatic investment with eyespan.

No description available.

This thesis describes a collection of experiments investigating sexual conflict and cryptic female choice in the Coelopidae. An experiment examining the effect of the alphabeta inversion karyotype in C. frigida revealed that male karyotype has no direct influence on male willingness to mate or other mating interactions, however, male size and karyotype have an influence over the female rejection response. There appears to be no clear genetic effect of female karyotype on female rejection behaviour, which leaves the question as to why alphaalpha females are mated with more often, unanswered. Females were found to mate hundreds of times in their lifetimes, making C. frigida an extremely promiscuous species with great potential for post-copulatory sexual selection to occur in this species. Evidence was found for cryptic female choice as females may have the ability to select sperm from within the ejaculate of a single heterokaryotypic male to produce fitter heterokaryotypic offspring. Time interval between copulations and the order of polyandrous copulations with males of different chromosomal karyotypes were found to interact in their effects on P 2values. The mating systems of 5 Australasian coelopids were examined and a comparative analysis of sexually antagonistic co-evolution in 13 coelopids was carried out. Female-mediated sexual conflict appears to have played a role in increasing male size and variation in male size, though large male reluctance to mate may mask evidence for antagonistic co-evolution. ISSRs were found to be a very useful tool in determining genetic variation in C. frigida and the possible future use of this technique in paternity analysis is discussed.

The literature relevant to mosquito genetics is first reviewed. In the present work, 51 different strains of Aedes aegypti have been examined for colour variation in particular. Methods of rearing, handling and routine are briefly described. Colour of the dorsal abdomen was so variable, that a scheme was devised to classify it, according to paleness, in 37 grades and sub- rades. These could be assiened to 15 numerical colour values to enable the paleness of a population to be quantitatively defined. Photography of variants was adopted as a routine. In Linkage Group I, two partially sex-linked factors controlling eye colour and one controlling abdominal colour were isolated, and 4 linkage distanoes determined. This is the first example of partial sex-linkage in A. aegypti and the first three-point, linkage estimation in any mosquito. In Linkage Group II one new mutant control ing thoracic colour was isolated and its recombination with the previously described s locus measured. At least 4 mutant alleles are shown to occur at the s locus sld one is identical with a gene previously ascribed to another locus. Two new mutants were isolated in Lirucage Group III and the crossover distance of one measured from the previously described blt locus at which a second mutant allele was isolated. A further three potentially useful mutants were obtained and other variation mentioned. The variation in abdominal colour in 39 strains is described and discussed. The frequency of genotypes in populations polyworphic for an s allele suggests,though not significantly, some degree of heterosis. Hybrids were successfully obtained between three pairs of Stego yia species. The relationship between A. aegypti and A. mascarensis, one of the two crosses giving fertile hybrids, is discussed more fully. A number of gynandromorphs and intersexes is also recorded.

No description available.

No description available.

Laboratory studies conducted on developing blowfly larvae (Diptera: Calliphoridae) showed that even small numbers of larvae resulted in an increase in temperature above ambient, and that they were able to retain heat when exposed to a lower ambient temperature. The increase in larval mass temperatures was also demonstrated in decomposition studies carried out on still-born piglets in London, where Calliphora vicina was dominant in an urban environment, and Lucilia sericata in a rural environment. Oviposition on indoor piglets was not always delayed, but may instead be delayed on outdoor cadavers if the ambient temperature is low. Decomposition studies were also carried out in Knoxville, Tennessee, on donated human cadavers. A body laid out on the ground attracted communal oviposition and larval mass temperatures up to 45°C. In contrast, a body placed in an unsealed plastic bin resulted in a delay in colonisation of seven days, with Phorids being the first flies to inhabit the cadaver, and blowfly oviposition delayed by ten days. The dispersal of post-feeding blowfly larvae from human cadavers was observed, and was found to be highly variable in direction, distance and time span. A further study was conducted to determine the length of time that empty pupal cases can remain in a natural woodland environment. The results suggested that depth of puparia and timespan are the important factors, and that after a period of three and a half years, the pupae are disintegrated and more difficult to locate and recover. Thermal imaging was also demonstrated as a useful tool in locating and measuring increased larval mass temperatures on both pigs and human cadavers. Benefits of using this method are that it is non-invasive and can be used to record and later analyse thermal images. Decomposition studies were carried out comparing pig and human cadavers. The results showed that the same species of blowfly are attracted to both types of cadaver, and oviposition sites, larval development and decomposition rates are also comparable, supporting the claim for pigs being a good substitute for humans in decomposition studies.

The thesis makes a distinct contribution to knowledge of both the systematics and the ecology of the species of psychodidae associated with aquatic habitats. The systematic work (Section I) was carried out as a necessary precursor to ecological investigation, aiming at the precise identification of every individual encountered. In this section there are descriptions of new species, and of previously unknown larvae and pupae; revised descriptions of other species, and some information on geographical variation. The problem or species pairs in the Family psychodidae is discussed at length. It is shown that Pericomu trivialize and P.nubila are true species, and that there are no grounds for considering these and the members of other species pairs as cases of male dimorphism, or any other than long established species. In section II an account is given of the ecology of the larvae and adults of species described in the first half of the thesis, considered from a number of new aspects. Several congeneric species normally occur together in the same breeding area, and although there is often a degree of spatial isolation between the larvae of these species, there are examples in which the larvae appear to live together in exactly the same microhabitat. Species of Pericoma and Telmatoscopus are all either univoltine, bivoltine or trivoltine, and there is a well defined seasonal succession of species. Larval adaptation is considered, with particular emphasis on the structure of the mouthparts. It is shown that the same adaptive features often arise independently in a number of separate evolutionary lines. Information is given on the adaptive significance of many structural characteristics, including reduction of setation, and the form of the mandible, labrum, hypostome and other mouthparts.

This thesis studies the effects of toxins upon larvae of the blowfly Lucilia sericata. A field study of fly populations infesting carcasses showed aggregations in space and time of a number of fly species, although L, sericata was not common. The presence of cadmium or deltamethrin in the larval diet was shown to have deleterious effects upon the larvae. Development was slowed down and the resultant adults were smaller. When the diet contained cadmium, adults had a lower fecundity than those arising from larvae fed upon the control diet. These effects became more pronounced as larval population density was increased. Models were constructed that simulated the population dynamics of L. sericata under two conditions. In each population, the larval diet was limited to 20 g/day whilst in one the diet was contaminated with 50 mg Cd/kg diet. These models allowed the underlying dynamics and their driving forces to be identified. The control model predicted sustained population cycles with a period of 67 days, approximately twice the generation time calculated from cohort life-tables. The cadmium model predicted that these cycles would be dampened and the mass of individual pupae increased relative to those from the control simulation model. These theoretical results, which apparently contradict the predictions made by scope for growth theory, are consistent with results from a long-term population study and were due to the interaction of cadmium with the effects of population density.