Chemical cuticular signature of leafcutter ant Atta sexdens (Hymenoptera, Formicidae) worker subcastes

ABSTRACT In leafcutter ants the division of labour is associated to worker size variation clustered in four subcastes. In this work we used Atta sexdens Forel (1908) as a model to test the hypothesis that each subcaste expresses its own chemical signature comprised of cuticular lipids. To assess it, we extracted epicuticular compounds by using nonpolar solvent hexane and analysed the samples in a combined Gas Chromatography-Mass Spectrometer (GC-MS). We found 24 hydrocarbons with carbon chains ranging from 19 to 39 atoms most of them classified as linear and branched alkanes. No compound occurred in the cuticle of specific worker subcaste, however, the relative proportion pattern varied greatly among them. Our results suggest that although subcastes have similar chemical signatures, significant differences in their relative proportions may play an important role between nestmate and group identification.

Comparison of radial growth rate of the mutualistic fungus of atta sexdens rubropilosa forel in two culture media

In vitro culture of the mutualistic fungus of leaf-cutting ants is troublesome due to its low growth rate, which leads to storage problems and contaminants accumulation. This paper aims at comparing the radial growth rate of the mutualistic fungus of Atta sexdens rubropilosa Forel in two different culture media (Pagnocca B and MEA LP). Although total MEA LP radial growth was greater all along the bioassay, no significant difference was detected between growth efficiencies of the two media. Previous evidences of low growth rate for this fungus were confirmed. Since these data cannot point greater efficiency of one culture medium over the other, MEA LP medium is indicated for in vitro studies with this mutualistic fungus due its simpler composition and translucent color, making the analysis easier.

EFICIÊNCIA DE ISCAS GRANULADAS À BASE DE SULFLURAMIDA E DE CLORPIRIFÓS NO CONTROLE DE Atta sexdens sexdens(HYMENOPTERA: FORMICIDAE), NO TRÓPICO ÚMIDO

This research was developed in hibrid urograndis (Eucalyptus urophylla Eucalyptus grandis)plantation belonging to Jari Celulose S.A., in Pará State, Brazil, from August 1994 to January 1995. The objective was to test one granulated bait with sulfluramid and three others with chlorpirifos in three dosages compared to 10 grams of dodecachlor (0.45%) bait per square meter of ant nest against Atta sexdens sexdens(Hymenoptera: Formicidae). The bait with sulfluramid showed 77.78%; 100.00%; and 88.90% efficiency against A. sexdens sexdensat 6, 8, and 10 grams while the dodecachlor bait showed 100.00% control. The other baits and dosages showed efficiency below 45.00%.

Este trabalho foi realizado em plantios de eucalipto urograndis (Eucalyptus urophylla Eucalyptus grandis)da Jari Celulose S.A., no município de Almeirim, Pará, no período de agosto/94 a janeiro/95. Foi testada a eficiência de uma isca granulada com sulfluramida e de três outras com clorpirifós, em três dosagens cada por metro quadrado de formigueiro, no controle de Atta sexdens sexdens(Hymenoptera: Formicidae). Os resultados foram comparados com os de uma isca à base de dodecacloro (0,45%) a 10 gramas por metro quadrado de formigueiro. A isca granulada com sulfluramida a 6, 8 e 10 gramas por metro quadrado de formigueiro apresentou 77,78%, 100,00% e 88,90% de controle, respectivamente, assemelhando-se à isca a base de dodecacloro que apresentou 100,00% de formigueiros mortos. As outras iscas, em qualquer dosagem, apresentaram eficiência abaixo de 45,00%.