Influence of the courtship song of the acridid grasshopper Gomphocerus rufus L. on the female

Summary Males of the acridid species Gomphocerus rufus L. perform unusually long courtship. Following their imaginal molt, the behavior of the females changes in three stages: initial rejection of the males, passive acceptance without singing, and active attraction of a mate by singing. Females in the active state permit copulation after brief courtship or even without it.To understand the function of long courtship, two hypotheses are tested by the present experiments. Hypothesis A assumes that the long courtship of the male affects the female so as to accelerate entry into the active mating state. This is not the case: Females raised in isolation enter the active state at the same time as those that have been exposed to courtship continually. Hypothesis B assumes that the long courtship changes the behavior of a female still in the passive state to enable earlier copulation. This hypothesis is tested by longterm recording of the locomotor and singing activity of the female in the presence of a courting male. The records show that the locomotor activity of a female in the passively acceptant state is significantly reduced during male courtship. Moreover, males in the presence of a passively acceptant female court longer than when the female is in either of the two other states.It appears, therefore, that the unusually long courtship serves to keep the female near the male for a longer period of time, increasing the chance of copulation. The advantages and disadvantages of this courtship strategy are compared with those of searching for a female in the active state.     

Chemical mimicry of cuticular hydrocarbons – how does Eremostibes opacus gain access to breeding burrows of its host Parastizopus armaticeps (Coleoptera, Tenebrionidae)?

Summary. Breeding burrows of Parastizopus armaticeps armaticeps, a fossorial desert tenebrionid beetle, are cleptoparasitised by the closely related Eremostibes opacus. Gas chromatographic analyses show a high congruity of the cuticular hydrocarbons of both species. We compare these hydrocarbon patterns with those of four other Stizopina species and the Scaurini Herpiscius sommeri. In a bioassay, dummies treated with cuticular hydrocarbon extracts of E. opacus and the P. a. bifidus parasite E. bushmanicus were mostly ignored by P. a. armaticeps, whereas dummies with applied extracts of the remaining species were heavily attacked. We show that there is a correlation between agonistic behaviour of P. a. armaticeps towards the intruder and the chemical similarity of the cuticular hydrocarbons of the two species. Furthermore, we produced quantitatively modified hydrocarbon patterns of E. barbatus by changing the temperature at which this species was kept. The new 30 °C type was chemically similar to E. opacus, and was frequently ignored by P. a. armaticeps, whereas a reduction of the temperature to 20 °C only had minor effects on the hydrocarbon pattern. Furthermore, we show that the addition of one single component, heptacosane, to the cuticular hydrocarbon extract of E. opacus alters the host’s reaction. We discuss the role of cuticular hydrocarbons for the recognition of this host-parasite system and the relevance of quantitative characters in the hydrocarbon pattern for the discrimination of the host.     

III. Ökotoxikologische Charakterisierung der Schwermetall-Immissionsmuster

The spatial variation of the immission patterns of Cr, Fe, Pb and V in the region Leipzig-Halle is dicussed in terms of similarities as well as dissimilarities. The representation by isopleths enables the identification of areas with high and low air pollution. The immission patterns can be used as criteria to select areas suitable for in-field testing so that possible effects on fauna und flora and xenobiotic fluxes can be studied at representative sites. The comparison with literature data yields a first characterization of the ecotoxic potential of the heavy-metal immission for the region. By the principal component analysis a comparative evaluation of the spatial structure of all element contents is performed, which leads to conclusions about emission sources and the physicochemical behaviour of the elements.