Adult emergence period, sex ratio, female calling behaviour, and the risky mating behaviour of A. aphidimyza in spider webs are described. We provide evidence that A. aphidimyza females produce a sex pheromone and attract males, and we give a description of the location and structure of the supposed pheromone producing glands of A. aphidimyza based on scanning and transmission electron microscopy. This is the first demonstration of occurrence of sex pheromones for a zoophagous species of Cecidomyiidae. The question is discussed why A. aphidimyza is using spider webs for mating.

In response to herbivory by insects, various plants produce volatiles that attract enemies of the herbivores. Although ants are important components of natural and agro-ecosystems, the importance of herbivore-induced plant volatiles (HIPVs) as cues for ants for finding food sources have received little attention. We investigated responses of the ant Formica pratensis to volatiles emitted by uninfested and insect-infested cucumber (Cucumis sativus) and potato (Solanum tuberosum) plants. Cucumber plants were infested by the phloem-feeding aphid Aphis gossypii, the leaf chewer Mamestra brassicae or simultaneously by both insects. Potato plants were infested by either Aphis gossypii, by the leaf chewer Chrysodeixis chalcites or both. In olfactometer experiments, ants preferred volatile blends emitted by cucumber plants infested with M. brassicae caterpillars alone or combined with A. gossypii to volatiles of undamaged plants or plants damaged by A. gossypii only. No preference was recorded in choice tests between volatiles released by aphid-infested plants over undamaged plants. Volatiles emitted by potato plants infested by either C. chalcites or A. gossypii were preferred by ants over volatiles released by undamaged plants. Ants did not discriminate between potato plants infested with aphids and caterpillars over plants infested with aphids only. Plant headspace composition showed qualitative and/or quantitative differences between herbivore treatments. Multivariate analysis revealed clear separation between uninfested and infested plants and among herbivore treatments. The importance of HIPVs in indirect plant defence by ants is discussed in the context of the ecology of ant-plant interactions and possible roles of ants in pest management.

1984.Behavior of Biornphcrltrritr glcrbratcr (Gastropoda: Pulmonata) under different lighting conditions. Can. J . Zool. 62: 2328 -2334. The preferred position, the surface contact area of the head-foot, and the locomotor activity of Biomphulariu glnbrcrtu were studied in a laboratory aquarium throughout the year. The snails were more frequently found on the walls and on the bottom than on the surface. Under two regimes of illumination their frequency of occurrences were different. The extent of the head-foot outside the shell increased from spring or summer to winter, and was significantly correlated negatively with temperature rather than illumination. Movement increased from summer to winter. Under artificial vertical lighting in the natural day cycle in group conditions two daily peaks become evident, at dusk and sunrise. Abrupt changes of illumination, especially during dusk, were discriminative cues for exogenous control of locomotion. Under constant darkness and in constant light, the level of locomotion was significantly lower than that under a natural day cycle of illumination, but in both regimes, locomotion was not significantly different; therefore, absolute illumination did not change the level of locomotion. In both regimes, snails were no longer synchronized to the solar rhythm. ' The threshold for natural light perception was around 20 Ix, when photokinesis appeared during the winter. Photokinesis increased with locomotion and both activities varied inversely with temperature.

Aquatic ecosystems are especially vulnerable to species introductions, because of their high degree of connectivity, ease of propagule dispersal, and intensive use as a transport route for materials, which aids species dispersal by shipping. In addition to these facilitating characteristics, certain activities also represent a potential opportunity for bioinvasions, and among these is the aquarium trade. The aquarium trade is considered one of the economic activities most closely linked to the dispersal of exotic species worldwide. Associated with this activity are reported invasions of seaweeds, fish, invertebrates, parasites, and pathogens; and without special care, the expansion of this sector will result in the spread of even more pests. In addition to the spe-Biological invasions currently represent one of the greatest worldwide threats to ecosystems. According to the Global Invasive Species Program (GISP), the introduction of species is the second greatest cause of loss of biodiversity on the planet, exceeded only by habitat degradation (Wittenberg and Cock, 2001; Simberloff, 2003). A survey by the MMA (2006) reported the confirmed occurrence of 49 invasive exotic species that affect continental waters, including crustaceans (1), aquatic macrophytes (6), microorganisms (1), molluscs (4), and fishes (37). However, other invasions of zooplankton organisms can be added to this preliminary list (