Parasitism and behavioral responses of Acromyrmex coronatus (Fabricius, 1804) and Acromyrmex crassispinus (Forel, 1909) (Hymenoptera: Formicidae) to Myrmosicarius catharinensis Borgmeier, 1928 (Diptera: Phoridae) in Londrina, PR

Abstract

Leaf-cutting ants of the genus Acromyrmex cause serious damage to cultivated forest areas. Some flies of the family Phoridae are known to parasitize them, and the result of this interaction can provide a promising basis for the management of these ants. This study was developed to record the parasitism and behavioral responses of Acromyrmex spp. leaf-cutting ants to parasitoid phorids in the municipality of Londrina-PR, Brazil. Visual examinations and collections of leaf-cutting ants and associated phorids were carried out between October/2019 and April/2020 in selected anthills and their trails, located on the campus of the State University of Londrina (UEL) and at the Botanical Garden of Londrina. The collected insects were preserved in 70% alcohol, for later identification of the species. The behavioral response of the ants to the parasitoids was recorded individually and collectively, following protocols cited in the literature. The frequencies of the different response behaviors exhibited by the attacked ants were compared using analysis of variance. The leaf-cutting ant species Acromyrmex coronatus and Acromyrmex crassispinus were found at the two evaluated sites. Myrmosicarius catharinensis was the only species of parasitoid phorid found, which attacked both ant species. Although the occurrence of M. catharinensis has been reported in other Brazilian states and its association with A. crassispinus recorded in Buenos Aires, Argentina, this is the first report of the occurrence of the phorid in the state of Paraná with a new association for the species A. coronatus. Under foraging action by the parasitoid, 63.5% of the ants exhibited only one behavioral response, while 36.5% showed two. Accelerated walking, attempting to “bite” the parasitoid, and adopting a ‘C’ posture were the most frequent behavioral responses to avoid parasitism. Ants crowding together around a worker and the presence of “hitchhiker” workers on the transported leaf fragments were the observed changes in collective behavior, the latter being the most frequent. These changes occurred in all observed ant nests and, in two of them, the constancy of alteration in collective behavior was 53%. These results demonstrate the interference caused in nests of Acromyrmex spp. by the occurrence of M. catharinensis, a potential control agent for this pest.