Mandibular gland chemistry of grass-cutting ants: species, caste, and colony variation.

The compositions of the alarm pheromones of two species of grass-cutting ant, Atta bisphaerica and A. capiguara, were examined, and caste and colony variations quantified. The pheromones of A. bisphaerica and A. capiguara were remarkably similar and were composed of a complex mixture of volatiles in which 4-methyl-3-heptanone and 2-heptanone were the most abundant compounds. Small but consistent intraspecific differences were found between the worker castes and between individual colonies. The results support the view that alarm pheromones are rarely species specific. The possible importance of intercolony variation is discussed.

Leaf surfaces and the bioavailability of pesticide residues.

Laboratory bioassays were carried out to determine the toxicity to Folsomia candida Willem (Collembola: Isotomidae) of residues of a pyrethroid insecticide, deltamethrin, and an organophosphorus insecticide, dimethoate, on different leaf surfaces. The test leaves included a range of species and leaves of different ages. Dose-response relationships were estimated for F candida walking over the various treated leaf substrates. Probit analysis was used to estimate the means and standard deviations of the associated tolerance distributions expressed as gAIha-1. Parallelism tests were undertaken to compare the susceptibilities of F candida to the two compounds applied to the different leaf surfaces. On deltamethrin-treated leaf surfaces, the LD50 values for F candida varied from 6.36 to 77.14 gAIha-1. F candida was least susceptible to deltamethrin residues when applied to leaves of dwarf bean (Phaseolus vulgarus L) and the highest susceptibility was observed following application to leaves of seedlings of barley (Hordeum vulgare L). In contrast, the LD50 values observed for dimethoate treatments did not differ significantly between leaf types, ranging from 1.35 to 8.69 gAIha-1. The laboratory data on susceptibility of F candida on different leaf types for different pesticides can be used to investigate the role of leaf surface properties in modifying the toxicity of applied pesticides to exposed invertebrates.

Evaluation of three (Z)-9-tricosene formulations for control of Musca domestica (Diptera: Muscidae) in caged-layer poultry units.

A field trial comparing the effectiveness of toxic targets impregnated with different formulations of the Musca domestica L. female sex pheromone (Z)-9-tricosene was conducted in a caged-layer, deep-pit poultry unit in southern England. Targets baited with 5 g of technical grade (Z)-9-tricosene, or 5 g of a 40% polymer bead formulation, caught significantly greater numbers of M. domestica than control targets. This increase in attractiveness of the pheromone-impregnated targets persisted for at least 24 wk. However, mean daily catch rates of M. domestica at targets baited with 5 g of a 2% wettable powder formulation did not significantly differ from control levels. Technical grade and bead formulations of the pheromone attracted significantly more males than females. However, the catches of female M. domestica at these pheromone-impregnated targets were significantly greater than female catches at control targets. Monitoring with sticky cards indicated that the introduction of toxic targets successfully suppressed adult M. domestica population density for up to 13 wk. Possible hypotheses explaining the effect of (Z)-9-tricosene on female attraction are discussed.

Evolutionary aspects of ant-fungus interactions in leaf-cutting ants.

Leaf-cutting ants are highly successful herbivores because they are able to use a wide variety of plants as food The workers harvest and process plant material to be used as substrate for a fungus on which they feed. New hypotheses concerning the evolution of the ant-fungus relationship have now been proposed. Although the relationship between the ants and the fungus is mutualistic, if may appear that the fungus has little control over the ants. However, evidence suggests that the fungus may be exploiting the ants to provide it with substrate and antimicrobial defence. Furthermore, experimental evidence suggests that the fungus can select its substrate by controlling the foraging behaviour of the ants, by means of an ingenious chemical feedback mechanism.

Repellent, toxic, and food protectant effects of pithraj,Aphanamixis polystachya extracts against pulse beetle,Callosobruchus chinensis in storage.

Ground leaves, bark, seeds, and four seed extracts of pithraj,Aphanamixis polystachya (family Meliaceae), a locally grown plant in Bangladesh, were evaluated for their repellency, contact toxicity, and food protectant efficacy against adult pulse beetle (Callosobruchus chinensis L.). The seed extracts showed poor repellent effects, but high contact toxicity to adults at 72 hr after application. The ground leaves, bark, and seeds provided good protection for mung beans against pulse beetles, and the seed powder greatly reduced the F1 progeny and seed damage rates.

Deterrent and insecticidal effects of extracts of pithraj,Aphanamixis polystachya (Meliaceae), againstTribolium castaneum in storage.

Laboratory experiments were carried out to investigate the efficacy of seed extracts of pithraj,Aphanamixis polystachya (Wall & Parker), a locally grown plant in Bangladesh, against the red flour beetle,Tribolium castaneum (Herbst.). Results of three different bioassays showed that crude extracts of pithraj seeds have strong repellent effects and moderate feeding deterrent and insecticidal (direct-contact) effects on adultTribolium castaneum.

Chemical composition of the frontal gland secretion ofSyntermes soldiers (Isoptera, Termitidae).

The defensive secretions from the frontal glands of soldier termites of the genusSyntermes contain similar mixtures of mono- and sesquiterpene hydrocarbons. The major components inS. dirus, S. molestus, S. brevimalatus, S. peruanus, and a new species (Syntermes sp. n), iscis-ß-ocimene. A substantial amount of aristolochene is found inSyntermes sp. n. and is present at lower levels in all the other species;S. brevimalatus contains onlycis-ß-ocimene and aristolochene. The four other species also contain minor amounts of epi-α-selinene and germacrene A. The latter compound has been identified on the basis of its rearrangement product ß-elemene. The termiteS. grandis differed markedly from the otherSyntermes species in that no terpenoid components were found in the soldier extract. With the obvious exception ofS. grandis, the same soldier-specific mono- and sesquiterpenes occurred in all species. The total amount of secretion per unit weight of soldiers varies with the species and is inversely proportional to the development of the mandibular apparatus. InS. molestus smaller gland size is compensated for by a greater number of soldiers foraging trails.

Variation in the temporal characteristics of the vocalizations of bullfinches, Pyrrhula pyrrhula.

Temporal characteristics of the vocalizations of bullfinches were investigated. The calls produced by experimentally isolated bullfinches were subjected to sonagraphic analysis. Within individual, between individual, and local variation in these calls was demonstrated. Several categories of calls were described, of which those termed "sequence calls" contained the greatest amount of information on which individual recognition could be based. Contact calls were individually distinctive in terms of their duration but with the exception of those produced by one female these lacked the structural complexity and information content of the sequence calls.