Search

The scarab beetle fauna (Coleoptera Scarabaeoidea) on Spotted Hyaena, Crocuta crocuta(Erxleben 1777), scats was investigated to identify the feeding guilds of scarabs on an unusual dung substrate. During 19 months inspecting hyaena latrines and surrounding roads, 69 specimens of 8 species of Scarabaeoidea (Trogidae and Scarabaeidae) were collected from 200 hyaena faeces samples and 17 samples of regurgitated hairs. With increasing amount of hairs in the samples, attraction to hyaena faeces increased (from dry, white faeces to soft, brownish faeces to regurgitated hairs). Most of the scarab species that we found feed generally on carrion and omnivore/carnivore dung. Three species have not previously been found on carrion but are likely to be (facultative) necrophages. Further records of beetles from hyaena faeces indicate that almost all species that are attracted by this bait are at least facultatively necrophagous. The dung part of their diet consists mainly of omnivore or carnivore faeces as is usual for necro-coprophagous species.

Summary Regulation of soldier development in termites at the endocrinological and social scale was intensively studied in the 60s and 70s, but conclusive results are still scanty. In termites, the presence of soldiers inhibits further soldier differentiation, but the mechanism is not well understood. Secretions from the frontal glands seem to be important, but dry- and dampwood termites do not have frontal glands. We investigated the influence of precocene I, a JH-antagonist, and of soldier head extracts on the development of soldiers in the drywood termite, Cryptotermes secundus (Hill). Soldierless colonies produced fewer soldiers when treated with precocene I or soldier head extract than control colonies. Furthermore, colonies treated with precocene I had produced worker-nymph intercastes, last stage nymphs and alates by the end of the experiment (after six months) which were not present in control colonies. Hence, both treatments inhibited soldier development while precocene I simultaneously promoted the development of adult traits, probably by reducing (directly or indirectly) the JH level. The inhibition effect of the soldier head extract indicates that at least in termites without a frontal gland, other sources of material in the head have a regulatory function.

In the past it has been demonstrated that the carbon concentration of large semi‐insulating (SI) GaAs single crystals grown by the conventional liquid encapsulation Czochralski (LEC) technique can be controlled by several methods including variations of growth parameters. It was the aim of the present paper to clarify which of the relationships of LEC growth could be used for a carbon control in the VCz‐method characterized by the application of an inner chamber made from graphite to avoid selective As evaporation. In detail this comprised a study of the influence of several growth parameters like the water content of the boric oxide, the composition of the working atmosphere, the gas flow, a titanium gettering and additions of gallium oxide. As a result, for the first time carbon concentrations down to ≈ 1014 cm‐3were obtained in 3'' (75 mm) diameter VCz crystals.

Molecular weight determinations of native and subunit RNAs of murine mammary tumor virus (MuMTV), a type B oncornavirus, were performed by polyacrylamide gel electrophoresis and compared with molecular weights of well-characterized avian cellular RNAs and tobacco mosaic virus RNA. From extrapolations of semilog plots of the molecular weights of the standard RNAs versus relative electrophoretic mobilities and Ferguson plots, the subunit and native RNAs of MuMTV were found to possess molecular weights of 2.93 X 10(6) and 6.45 X 10(6), respectively. These data support the assumption that two subunit molecules comprise the native RNA of MuMTV.

The three species of single-stranded RNA present in La Crosse virus were examined in the electron microscope. Because large amounts of contaminating cellular DNA are copurified with the virus despite extensive attempts to purify the virus, it was necessary to use procedures that eliminated the bulk of this DNA before the viral RNA was analyzed. When this was done, the modal lengths of La Crosse virus RNA were 0.4, 2.0, and 3.1 mum. These lengths correspond well to their known molecular weights of 0.4 x 106, 1.8 x 106, and 2.9 x 106. Under the denaturing conditions used to permit complete spreading of these single-stranded RNA molecules, no single-stranded circular molecules are observed. Therefore, the circular nucleocapsids present in La Crosse virus and some other bunyaviruses do not appear to be due to convalent linkage of the ends of the RNA genome.

In the Guinea Savanna Zone of the Ivory Coast (Côte d'Ivoire) the dragonfly Crocothemis divisaKarsch 1898 survives the dry season as sexually inactive adults. Both sexes use mounds of the termite Macrotermes bellicosus(Smeathman 1781) as daytime resting sites. Individuals were often observed to aggregate on a few particular mounds, while the majority of mounds remained unoccupied. The insects, which perch in the shade on the ribs of the steep mound sides, repeatedly change their positions during the course of the day in response to direct solar illumination. Flights are very short and not accompanied by the aggressive behaviour typical of sexually active individuals. The choice of termite mounds is compared with this species' known preference for bare perches and is considered to be of importance for thermoregulation and to reduce the risk of predation.

The Kalotermitidae is a family of lower termites and its species are ideal to study the evolution and maintenance of eusociality within the Isoptera. Co-dominant genetic markers are an essential tool to elucidate the putatively complex colony and population structure. Six polymorphic microsatellite loci were identified in the drywood termite Cryptotermes secundus (Kalotermitidae). To test the variability of the markers, 18 colonies (n = 18) from Darwin (Australia) were assayed. We found two to eight alleles per locus with the level of observed heterozygosity at each locus ranging from 0.00 to 0.53. The significantly positive FIT value suggests that some kind of inbreeding does occur in this population.