Bioindicadores ambientais: insetos como um instrumento desta avaliaçãoAtividades agrícolas, florestais e do setor imobiliário vêm, ao longo do tempo, modificando ambientes ecologicamente estruturados. As consequências são drásticas e, por isso, faz-se necessária a busca por ferramentas e instrumentos para diagnosticar e monitorar a diversidade biológica desses locais. Os insetos têm-se destacado como potenciais organismos bioindicadores e isso se deve ao fato de apresentarem grande capacidade perceptiva, no que se refere a alterações do meio ambiente, principalmente por seu apurado sistema sensorial, que lhes permite qualificar condições ambientais em determinadas situações e, ainda, quantificar danos causados ao meio. Um dos problemas que podem ser associados a este setor é a falta de padronização e definição de protocolos de coleta e avaliação da biodiversidade, para que esses resultados possam ser analisados e extrapolados para diferentes ambientes antropizados. Neste trabalho, é contextualizada a importância da entomofauna como bioindicadora, em ecossistemas. Palavras-chave:Biodiversidade, bioindicadores, impacto ambiental, insetos.

ABSTRACT

Atta bisphaerica (Forel) is a leaf-cutting ant that specializes on grass and causes productivity losses in sugar cane fields and pastures. Three phorid species, Apocephalus attophilus (Borgmeier), Myrmosicarius grandicornis (Borgmeier) and Eibesfeldtphora bragancai (Brown), have been found parasitizing A. bisphaerica workers. These parasitoids can reduce plant material transported into the nests and ant traffic on the trails. Therefore, phorid flies have been considered potential biological control agents for leaf-cutting ants. Here, we evaluated which parasitoid species attack the leaf-cutting ant A. bisphaerica in pasture areas of a Brazilian Savannah-Atlantic Forest ecotone, parasitism rate, effect of host size, sexual dimorphism and sex ratio of the emerged parasitoids. Four nests of A. bisphaerica were selected in pasture areas from August 2016 to August 2017, with 400 workers collected from each colony monthly. A total of 23,714 A. bisphaerica workers were collected during the study, of which 236 (0.99%) were parasitized by phorid parasitoids. Apocephalus attophilus, E. bragancai and M. grandicornis parasitized 217, 17 and 2 ants, respectively. The higher parasitism rate was found in the hottest/rainy season of the year. Non-parasitized ants survived longer than those parasitized by A. attophilus. The larval and pupal periods of this parasitoid were 2.2 ± 0.8 and 16 ± 1.4 days, respectively, and the number of pupae per parasitized ant ranged from 1 to 7. The number of A. attophilus pupae per host increased with the host head size. Likewise, the size of the adult parasitoids also increased according to the host ant. Apocephalus attophilus females were larger than males and the sex ratio (male: female) did not differ from 1: 1. Our results showed that A. attophilus would be a potential biocontrol agent of leaf-cutting ants because it produces multiple larvae per host, allowing a great production of parasitoids with short developmental time and kills the host ant faster than other phorids.

The leaf-cutting ant Atta sexdens Forel (Hymenoptera: Formicidae) is one of the most damaging agricultural pests in the Neotropics. Management strategies predominantly rely on the use of general insecticides. What is needed are more species-specific and environmentally friendly options. Parasitioids such as phorid flies (Diptera: Phoridae) may be one such option, but a greater understanding of the ecology of the flies and their ant hosts is essential to devise biological control strategies. Here we report parasitism rates, ant host size, parasitoid abundance per host and resultant sex ratios of two phorid species Apocephalus attophilus Borgmeier and Eibesfeldtphora tonhascai Brown parasitizing A.sexdens. The two species achieved parasitism rates of 1.48 and 1.46%, respectively and the pupal period was 14.7 ± 1.1 days and 22.1 ± 2.8 days, respectively. There was no significant difference between the head capsule width of ants parasitized by either A. attophilus or E. tonhascai. Likewise, there was no significant effect between the head capsule width of parasitized and unparasitized ants for both species. A significant positive correlation was found between the head capsule width of the parasitized ants and the number of adult parasitoids A. attophilus emerged. Ants parasitized by E. tonhascai survived significantly longer than those parasitized by A. attophilus. There was no significant effect of ant head width on the sex ratio of the offspring of either parasitoid species and no significant difference in the sex ratio (male: female) of their offspring. In summary, these data addressed here are important steps when considering natural enemies for biological control. Studying survival of the parasitized ants, parasitoid offspring sex ratio and host size preference allows for a better understanding of ant natural biological control in the field and can help in rearing of A. attophilus and E. tonhascai in laboratory.

Neotropical Entomology 36(4): 510-513 (2007) Morfologia do Percevejo Fitófago Platyscytus decempunctatus (Carvalho) (Heteroptera: Miridae) RESUMO -Platyscytus decempunctatus Carvalho é um mirídeo de pequeno porte que vive durante seu ciclo de vida em plantas de Solanum cernuum Vell. (Solanaceae). A morfologia interna de P. decempunctatus foi estudada revelando que fêmeas possuem ovário do tipo telotrófico com três ovaríolos no ovário direito e cinco no esquerdo. Nas estruturas reprodutivas dos machos existe uma glândula acessória tubular bem desenvolvida. A fitofagia de P. decempunctatus foi confirmada devido a observações de pigmentos de clorofila no intestino de todos os espécimes dissecados. As glândulas salivares em formato tubular e os túbulos de Malpighi também foram discutidos. PALAVRAS-CHAVE: Ovário, testículo, tubos de Malphigi, glândula salivar, Solanum cernuumABSTRACT -Platyscytus decempunctatus Carvalho is a small mirid living throughout its life cicle plant Solanum cernuum Vell. (Solanaceae). The internal morphology of P. decempunctatus was studied and found that the female has a telotrophic ovary with three ovarioles in the right ovary and five in the left one. In the male reproductive trait there is a well developed tubular accessory gland. The phytophagous feeding habitat of P. decempunctatus was confirmed by the observations of chlorophyll pigments in the gut of all dissected specimens. The tubular salivary glands and the Malpighian tubules were also discussed.

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Pre-release techniques aim to increase the searching by the predators for their prey. Keeping bug predators for periods without food before their release can increase the search ability of these insects. However, this practice can increase the cannibalism during mass rearing. Brontocoris tabidus (Signoret) and Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) were kept for 12, 24, 36 and 48 h without food or with only Eucalyptus cloeziana plants in order to verify the occurrence of cannibalism on adults and eggs. Insects kept for periods longer than 24 h showed higher cannibalism on adults and eggs and the presence of a E. cloeziana plant decreased the cannibalism during all the treatment periods. These predators preferred to attack first the eggs rather than the adults, probably because of the inability of the former to avoid predation. The pre-release period should not exceed 24 h and plants must be provided to the predators in order to reduce the occurrence of cannibalism and increase the predatory capacity of these natural enemies.