Objetivou-se avaliar a eficiência de estratégias de artrópodes contra a predação por formigas. Realizamos simulações de estratégias anti-predatórias para testar as seguintes hipóteses: esconder-se entre os componentes da serapilheira é uma boa estratégia para um artrópode evitar a predação por formigas; a estratégia de alguns artrópodes de manterem-se suspensos por um fio é eficaz contra predação; variações na estratégia de manter-se suspenso afetam sua eficiência; a predação varia com a altura da presa em relação ao solo. Realizamos dois experimentos numa floresta secundária em Angra dos Reis-RJ. No primeiro, a serapilheira foi removida de parcelas e aplicou-se os seguintes tratamentos: exposto (um grão de arroz sobre o solo); uma folha (um grão de arroz entre o solo e uma folha); duas folhas (um grão de arroz entre duas folhas); quatro folhas (um grão de arroz entre quatro folhas). No segundo, utilizou-se os seguintes tratamentos: suspenso – um fio preso em dois galhos de plantas e um grão de arroz fixo na ponta de um segundo fio, criando uma estrutura em forma de “T”; pêndulo – um fio preso a um galho e na outra extremidade um grão de arroz; folha - um grão de arroz sobre uma folha; serapilheira – um grão de arroz sobre a serapilheira. O suspenso e o pêndulo mostraram-se eficazes, mas o suspenso foi mais eficiente. A altura da isca em relação ao solo não influenciou probabilidade de ocorrer a remoção. Esconder-se entre componentes da serapilheira pode ser um mecanismo de defesa eficiente contra a predação por formigas.Arthropod Strategies Against Predation by Ants in a Secondary Forest in Rio de Janeiro, BrazilAbstract. We assessed the efficiency of arthropod strategies against predation by ants. Simulations of anti-predator strategies were carried out to test the following hypotheses: hiding in the leaf litter is efficient to escape predation by ants; hanging by a thread is also efficient against ants; variations in the strategy of hanging by a threat affect its efficiency; predation depends on the height of the prey from the ground. We carried out two experiments in a second-growth forest in Angra dos Reis, southeastern Brazil. In the first experiment, leaf litter was removed from the plots and we exposed rice grains to four treatments: a rice grain on the ground (exposed); a rice grain between the ground and a leaf (one leaf); a rice grain between two leaves (two leaves); a rice grain between four leaves (four leaves). In the second experiment, we used other four treatments: a thread attached to two branches of a plant and a second thread hanging from it, with a rice grain attached to its extremity, forming a T-shaped structure (hanging); a thread attached to a branch, with a rice grain attached to its other extremity (pendulum); a rice grain on a leaf (leaf); a rice grain on the leaf litter (leaf litter). Hanging was more efficient than pendulum; though these both strategies showed to be efficient. The height of the bait above ground did not affect its removal probability. Hiding in the leaf litter can be considered as an efficient defense mechanism against predation by ants.

Este trabalho objetivou testar a hipótese de que formigas com menor tamanho corporal têm maior sucesso em explorar os interstícios do ambiente, enquanto que ambientes menos rugosos favorecem formigas com tamanho maior. O experimento foi realizado em uma floresta secundária situada no distrito de Ilha Grande, Angra dos Reis-RJ (23º11’01’’S, 44º 11’44’’W). Foram escolhidos ao acaso 14 locais distantes 10 metros entre si. Em cada local foram demarcadas três parcelas de 50cm x 50cm com espaçamento de 10cm entre si. A serapilheira foi removida das parcelas e aplicou-se tratamentos que simularam ambientes com diferentes níveis de rugosidade: baixo (sem serapilheira); médio (somente folhas de bambu); e alto (com serapilheira). Iscas de sardinha e solução de água com açúcar foram colocadas no centro de cada parcela e a primeira formiga que alcançou as iscas foi coletada. O comprimento total do corpo das formigas coletadas foi significativamente menor no tratamento com maior nível de rugosidade (Teste de Tukey, p < 0,05). Os resultados confirmaram a hipótese de que formigas menores são favorecidas em ambientes com alto nível de rugosidade.Testing the Size-grain Hypothesis: Influence of the Environmental Rugosity on Ants (Hymenoptera: Formicidae)Abstract. This study aimed to test the hypothesis that smaller ants are more successful in exploring environmental interstices than larger ants, whereas environments with less rugosity are better for larger ants. The experiment was conducted in a secondary forest located in Angra dos Reis, Rio de Janeiro State (23 11’00’’S, 44 11’44’’O). Fourteen sites were randomly selected and in each site three plots (50cm x 50cm) were demarcated. The leaf litter was removed from the plots and were applied treatments that simulated environments with different rugosity levels: low (no leaf litter), medium (only bamboo leaves) and high (with leaf litter). Food baits were exposed in the center of the plots and the first ant that access the baits was collected. The total length of the ants was significantly lower in the treatment with higher level of rugosity (Tukey, p <0.05). The results confirmed the hypothesis that environments with high levels of rugosity favours smaller ants.

The objective of this study was to assess if larvae of Phylloicus spp. show any preference for leaves with or without microorganisms when building cases. Two experiments were realized at municipality of Presidente Figueiredo (Amazonas – Brazil), containing leaves treated with Hydrogen peroxide (H2O2), a compost that has an antimicrobial action, and another one with untreated leaves. In the first were observed the case-building by larvae of Phylloicus spp. and in the second was tested the preference by treated or untreated leaves. The larvae were monitored during 24 hours and to statistical analysis was used the t-test. Were not observed significant differences in the number of discs used by the larvae in the first experiment (p=0.24; t=-0.73) and no preference by type of leaf in the second experiment (p=0.41; t=0.23). Therefore, we do not recommend the use of hydrogen peroxide in studies that aim to eliminate microorganisms from decomposing leaves.