Summary 1.A before/after-control/impact experiment (BACI) was used to examine the shortterm effects of canopy openness on insect herbivores foraging on the seedlings of five rain forest species in an unlogged forest in Guyana. During the first and second study years, insects were collected monthly from 250 sites, representing 9750 seedlings spread over a plot of 1 km 2 . At the onset of the second collecting year, half of the parent trees at the sites were felled, creating an average canopy openness of 26%. 2. Comparisons of the control and impact sites before and after the felling showed that overall insect abundance, particularly of psyllids, and species richness increased at the impact sites, whereas evenness decreased markedly. These responses were consistent with the prediction that intermediate disturbance promotes high diversity in tropical systems. 3. Twenty-nine per cent of insect species analysed showed a significant response to felling, with some populations doubling or halving at the impact sites after felling. The abundance of most species increased, although responses varied even between congeners. 4. A canonical correspondence analysis at the impact sites after felling indicated that most species responded to an increase in leaf production by seedlings, not to canopy openness per se . Species declining at the impact sites were more likely to feed indiscriminately on young and mature foliage and probably reacted to changes in microclimate. 5. The study illustrates the difficulty in identifying higher taxa, umbrella or indicator species that adequately integrate the responses of insect herbivores to forest disturbance. Because the integrity of insect communities in the understorey of this forest depends more on minimizing damage to plant resources than on canopy openness, we found some support for the conservation value of reduced impact logging in tropical wet forests.

To study vertical gradients of arthropod species richness in tropical forests, adult chrysomelids were surveyed with similar sampling effort by beating in four plots of 0.8 ha, representative of the canopy and understorey of one wet and one dry forest in Panama. Samples included in total 4615 individuals representing 253 species, and were of similar species richness at the two study sites. At both sites, chrysomelids were significantly more species-rich in the canopy than in the understorey. The proportion of species shared between the two study sites was 24%, whereas 16% and 28% of species were shared between the canopy and understorey of the wet and dry sites, respectively. Mature trees supported more and different chrysomelid species than conspecific saplings. A higher proportion of liana feeders vs. tree feeders occurred at the dry site than at the wet site. Multivariate analyses confirmed the faunal differences between the wet and dry sites and that stratification was more marked at the wet site than at the dry site. The latter observation may relate to differences in forest physiognomy (a tall and closed canopy at the wet site) and to the high interconnectivity via lianas between the understorey and canopy at the dry site.

An. Soc. Entomol. Brasil 29(3): 433-452 (2000) Lista Comentada de Insetos Herbívoros Encontrados em Plântulas de Cinco Espécies Florestais na Guiana RESUMO -Uma lista de insetos herbívoros de vida livre colecionados em plantas de cinco espécies de importância econômica, perto de Mabura Hill, Guiana é apresentada. As plantas hospedeiras incluem as seguintes espécies: Chlorocardium rodiei (Scomb) (Lauraceae), Mora gonggrijpii (Kleinh) Sandw. (Caesalpinaceae), Eperua rubiginosa Miq. (Caesalpinaceae), Pentaclethra macroloba (Willd.) Kuntze (Leguminosae) and Catostemma fragrans Benth. Bombacaceae). Cerca de 10.000 plântulas foram observadas com intervalos de um mês durante dois anos. Durante este período, 27.735 insetos pertencentes a 604 espécies foram colecionados. Os insetos mastigadores de folhas foram testados no laboratório, com a finalidade de identificar as espécies não herbívoras e as ocasionais. Os insetos sugadores mais comuns e abundantes são: Psyllidae, Cicadellidae, Derbidae, Membracidae, Achilidae; Galerucinae, Eumolpinae, Alticinae, Cryptocephalinae, Gelechiidae e Entiminae (insetos mastigadores de folhas). As espécies mais comuns (n ≥ 22 indivíduos) são generalistas. Ao início do segundo ano de coleta, metade das árvores mães ("estações", n=125) foram selecionadas para ser cortadas, imitando o processo madeireiro. Apresentase um teste preliminar comparativo da abundância das espécies mais freqüentes durante os dois anos de coleta, assim como entre as estações cortadas e as não cortadas. Os resultados sugerem que perturbações leves podem aumentam a abundância de apenas algumas espécies. Estes padrões não parecem ser similares para espécies congenéricas. Esta investigação visa fornecer informações para o parco estudo da entomofauna herbívora em plântulas numa floresta húmida tropical. PALAVRAS-CHAVE: Insecta, Catostemma, Chlorocardium, Eperua, floresta húmida. ABSTRACT -An annotated list of the free-living insect herbivores collected 434 Basset & Charles on the seedlings of five rainforest tree species of economic importance near Mabura Hill, Guyana, is presented. The host plants were Chlorocardium rodiei (Scomb.) (Lauraceae), Mora gonggrijpii (Kleinh.) Sandw. (Caesalpiniaceae), Eperua rubiginosa Miq. (Caesalpiniaceae), Pentaclethra macroloba (Willd.) Kuntze (Leguminosae,) and Catostemma fragrans Benth. (Bombacaceae). During the monitoring of approximately 10,000 seedlings at monthly intervals during two years, 27,735 insect individuals were collected representing 604 species. Leaf-chewing insects were further tested in captivity, to remove transient and non-feeding species. The most common higher taxa included Psyllidae, Cicadellinae, Derbidae, Membracidae and Achilidae for sap-sucking insects and Galerucinae, Eumolpinae, Alticinae, Cryptocephalinae, Gelechiidae and Entiminae for leaf-chewing insects. Most of the common species collected (n ≥ 22 individuals) were generalists. At the onset of the second collecting year, half of the parent trees ("stations", n = 125) were felled to mimic selective loggin...

A brief outline of entomological activities in the rain forests of French Guiana, Guyana and Suriname, is presented. The information available on the main groups of sap-sucking (Thysanoptera and Heteroptera) and leaf-chewing (Phasmids, Orthoptera, Coleoptera, Diptera, Lepidoptera and Hymenoptera) insects is discussed. Leaf damage (herbivory) and leaf-cutting ants are described.

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