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To investigate the causes of striking sexual dimorphism in the harlequin beetle (Acrocinus longimanus), we carried out a study of the behavior and morphology of two widely separated populations (in French Guiana and Panama). Males of this species possess greatly elongated forelegs which exhibit strong positive dometry with body size (elytra length). Males use their forelegs in fights with other males and in guarding females and oviposition sites. Field data on fighting and mating success suggest that sexual selection favors large size in males. However, the direct targets of selection were masked by high correlations between traits of the elytra, forelegs, and antennae. Sexual selection appears to be driven by intense male competition to monopolize suitable sites for egg deposition. Female harlequin beetles are highly selective in choosing only recently dead or dying trees for oviposition (Moraceae and Apocynaceae). Despite marked geographic variation in coloration, host trees, and dimate, the two populations did not differ in mean size and extent of sexual dimorphism. We suggest that sexual selection in this species is sufficiently intense to override any effects of differing ecological factors.

Estimates of the total number of arthropod species in existence are based, in part, upon assumptions about both the host specificity of tropical insects and their restriction to the forest canopy. It has been difficult to evaluate these estimates because of the paucity of available data. A newly discovered association between wood-boring beetles (Cerambycidae) and their host plants in the Brazil nut family (Lecythidaceae) inspired a year-long rearing project in the Neotropical rain forest of French Guiana. Branches severed from five species of Lecythidaceae yielded 1813 cerambycids belonging to 37 species. Three cerambycid species-Palame anceps (Bates), II crassimana Bates, and P mimetica Monne-accounted for almost half of the individuals reared. Each demonstrated a different pattern of host fidelity.Palame crassimana emerged from four of the five potential hosts, II anceps emerged exclusively from a single host, and P mimetica made a seasonal change in host affiliation. Although Palame spp. emerged from both ground level and canopy branches, they made a seasonal shift in stratum: they reproduced at both levels during the dry season, but exclusively at canopy level during the rainy season. Even specialized tropical insects may show greater flexibility in host utilization than some current hypotheses suggest. 0 1999 The Linnean Society of London ADDITIONAL KEYWORDS:-host specificity -canopy arthropods -forest stratuminsect seasonality -insect-plant interactions -Couratari stellata -Eschweilera coriacea -Gustavia hexapetala -LqthW. poiteaui.

Heteroglenea Gahan, 1897 is reinstated from the synonyms of Glenea (sensu stricto) Newman, 1842, and is redefined. Four taxa are transferred to Heteroglenea: H. fissilis (Breuning, 1953) comb. nov., H. bastiensis (Breuning, 1956) comb. nov., H. momeitensis (Breuning, 1956) comb. nov. and H. mediodiscoprolongata (Breuning, 1964) comb. nov. Glenea mimoluctuosa Breuning, 1968 is considered a junior synonym of H. mediodiscoprolongata (Breuning, 1964). Glenea (G.) palawana Breuning, 1956, G. (G.) guadalcanalana Breuning, 1958, and G. (G.) hamabovola Hayashi, 1975, are considered junior synonyms of H. glechoma (Pascoe, 1867). Heteroglenea vicinalis Lin et Yang sp. nov. from Nepal and India, H. gemella Lin et Yang sp. nov. from Nepal and H. dolosa Lin et Yang sp. nov. from Laos are described. Heteroglenea fissilis and H. mediodiscoprolongata are newly recorded from China. Photographs of habitus and terminalia and a key to the nine valid species of Heteroglenea are presented.

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