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The eggs of 21 species in 12 genera of Sepsidae were studied using scanning electron microscopy. All but the eggs of Ortalischema have respiratory filaments which aid in gas exchange. Judged by positional differences and the lack of a central canal, the two filaments of Orygma are not homologous to the single filament of most remaining sepsids. Hinton's hypothesis that egg filaments are plesiomorphic for the Sepsidae is therefore rejected. Three egg characters are added to an existing data set comprising 58 taxa and 85 larval and adult characters. The egg characters allow the unambiguous placement of Lasionemopoda, for which the larval and adult data set had suggested two different positions on equally parsimonious trees. Based on the position of Lasionemopoda, the evolution of the fore femora of the Sepsidae is briefly discussed. The egg morphology of the Sepsidae is also compared to the morphology of drosophiline eggs which also have egg filaments.

The empirical performance of the ontogenetic criterion for determining character po- larities was tested based on three published and one new data set originating from a study of larval Sepsidae (Diptera). The ontogenetic criterion polarizes about as many characters as does outgroup comparison. However, for the four data sets conflicting polarities were inferred for 4- 45% of all characters for which both polarization methods were applicable. Four different versions of the ontogenetic criterion were identified from the literature and were empirically tested. The version used by de Queiroz (1985, Syst. Zool. 34:280-299) and Wheeler (1990, Cladistics 6:225- 268) fared best, as determined by low levels of homoplasy and a small number of inferred equally parsimonious tree roots. For three of four empirical data sets, hypothetical ancestors based on outgroup comparison and the ontogenetic criterion resulted in identical tree roots. Hypothetical ancestors based on outgroup comparison implied less homoplasy than did those based on the ontogenetic criterion, so the ougroup method appears to be superior for character polarization. To test whether polarity decisions from both polarization methods should be combined into one hypothetical ancestor, two different "composite" ancestors were reconstructed. One comprised only the plesiomorphic states of the characters for which both criteria predicted the same polarity (consensus). It inferred multiple parsimonious roots without distinctly lowering the level of ho- moplasy. The second ancestor comprised the plesiomorphic states as predicted by one or both methods (composite). It tended to infer single roots, even for data sets for which very different rooting positions were identified by the two polarization criteria, thereby obscuring conflict be- tween the two methods. High levels of homoplasy in hypothetical ancestors based on the onto- genetic criterion are not due to the inclusion of presence /absence characters in the data set, for which the application of the ontogenetic criterion would require hypotheses of homology for "absent" character states across ontogenetic stages of different species. Instead, the ratio of ter- minal deletions to terminal additions is a better predictor for the success of the ontogenetic cri- terion for any particular data set. (Biogenetic law; heterochrony; Nelson's rule; ontogenetic crite- rion; outgroup comparison; recapitulation.)

Journal of Insect Science, 9 (1), ISSN:0970-3837, ISSN:1536-2442

Even for the most cosmopolitan of species, climate frequently presents effective barriers for dispersal. For example, many eurytopic and synanthropic species go extinct when introduced into a new climatic zone, and translocated ants remain in sheltered environments reminiscent of their home climate (McGlynn, 1999). Here we report the occurrence of a primarily Holarctic dipteran species, Themira leachi (Meigen), in Neotropical Cuba. This discovery suggests that the species may have a large disjunct distribution, as the next closest record lies almost 3,500 km to the north in Nearctic Newfoundland, Canada (Ozerov, 1998).

SOME species of Diptera utilize freshly dropped cattle dung (cow pats) not only as an oviposition site and larval habitat but also as a male aggregation site where mating occurs1,2. The present investigation shows that the males of some of these species protect their mates, thus preventing the mating activity of the preponderant and aggressive unpaired males from interfering with oviposition. Such co-operative behaviour is most striking in the cosmopolitan yellow dung fly, Scatophaga stercoraria (L.) (Anthomyiidae), but also exists in Saltella sphondylii (Schrank) (Sepsidae) and Copromyza atra (Meigen) (Sphaeroceridae); these three species are closely related only in an ecological sense.

Comparison of the distributions of Sepsidae using, inter alia, numerical methods shows that the Australian fauna includes three groups of species: (1) southern temperate (cool-adapted), endemic to Australasia; (2) northern tropical (warm-adapted). also endemic to Australasia; (3) northern tropical widely distributed in the Oriental Region also. Analysis of seasonal occurrence yields a different grouping, two species of Sepsis showing an anomalously early (and still unexplained) peak of abundance in spring. It is considered likely that group 1 above represents stocks that reached Australia well before the Pleistocene, one of them later spreading to New Guinea; species in group 2 originated in or near New Guinea, migrating to Australia in, perhaps, the Pleistocene; and those in group 3 are of Oriental origin, having reached Australia at various times during or since the Pleistocene; some may be quite recent arrivals.

Background In a number of species males damage females during copulation, but the reasons for this remain unclear. It may be that males are trying to manipulate female mating behaviour or their life histories. Alternatively, damage may be a side-effect of male-male competition. In the black scavenger or dung fly Sepsis cynipsea (Diptera: Sepsidae) mating reduces female survival, apparently because males wound females during copulation. However, this damage does not seem to relate to attempted manipulation of female reproduction by males. Here we tested the hypothesis that harming females during mating is an incidental by-product of characters favoured during pre-copulatory male-male competition. We assessed whether males and their sons vary genetically in their ability to obtain matings and harm females, and whether more successful males were also more damaging. We did this by ranking males' mating success in paired competitions across several females whose longevity under starvation was subsequently measured. Results As previously reported, our results show mating is costly for female S. cynipsea. However, variance in female longevity was not explained by male identity, family, body size, number of previous copulations, or copulation duration. Nevertheless, there was a positive correlation between the harm fathers inflicted on their mates (affecting female longevity) and the harm sons inflicted on theirs. Additionally, family identity significantly influenced male copulation success. Conclusion Our results indicate a heritable component of some yet unspecified male trait(s) that influence harm and mating success. However, there was no relationship between copulation success of fathers or sons and the mean longevity of their mates. We therefore found no support for harm being a side effect of traits favoured in pre-copulatory male-male competition.