Differential parasitism by four species of phorid flies when attacking three worker castes of the leaf-cutting ant Atta laevigata (Smith, 1858)

Abstract

Certain species of parasitic flies belonging to the Phoridae are known to attack Atta spp. workers foraging along trails, near nest openings used by the ants to supply the colony with plant material, and in the areas where the ants are actively cutting plant material. However, there have been no previous studies of phorid parasitism of non-foraging worker ants, for example excavators and soldiers. Excavators can be found on the surface around specialized nest openings, carrying and dumping soil on characteristic mounds. Soldiers can be found on the trails protecting foragers or guarding the different types of nest openings. The current study was performed to investigate the differential parasitism rates of Atta laevigata (Smith, 1858) worker castes by four species of phorids. Ants of all castes on trails and at nest entrances were collect from 18 mature colonies in the field. A total of 21,254 ants were collected from trails and 14,649 collected from the mounds of loose soil near nest openings. The captured workers were maintained under controlled laboratory conditions to evaluate the rate of parasitism. Of the ants collected from trails, 1,112 (5.23%) were found to have been parasitized, of which 1,102 were foragers and only 10 were soldiers. Of the ants collected from the soil mounds near the nest openings, only 27 (0.18%) were found to have been parasitized, of those 25 were excavators and 2 were soldiers. When evaluating parasitism of ants on the trails, 46.2% were attacked by Apocephalus attophilus Borgmeier, 1928, 22.6% by Myrmosicarius grandicornis Borgmeier, 1928, 16.6% by Eibesfeldtphora erthali (Brown, 2001) and 14.6% by Apocephalus vicosae Disney, 2000. Only two species of phorid, M. grandicornis and E. erthali, were observed parasitizing excavators, whilst only E. erthali parasitized soldiers. This is the first time that Atta spp. excavators and soldiers have been shown to be parasitized by phorids. The low rates of parasitism and specificity of certain phorid species for excavators and soldiers is discussed in relation to the behavioral interactions of hosts and their parasitoids, as well as the relationship between host and parasitoid size.

Phorid parasitoids of the leaf‐cutting ant Atta laevigata in the Atlantic Forest: occurrence, parasitism rate, and host size

“…Three to five was a frequent number of A. attophilus flies emerging from parasitized ants, but some host produced up to 17 flies. The highest number of flies by host ever reported in A. laevigata was 14 (Souza et al, 2021; Bragança, 2011), but 17 flies has already been reported for A. sexdens (Galvão et al, 2019). Bragança et al (2016) reported cases of A. laevigata foragers simultaneously parasitized by A. attophilus and A. vicosae (0.0055%); however, we detected no case of multiparasitism.…”

The Biology of <i>Szelenyiopria talitae</i> (Hymenoptera: Diapriidae): Larval Parasitoid of the Leaf-Cutting Ant <i>Acromyrmex subterraneus</i> (Hymenoptera: Formicidae)

“…The study of host-parasitoid interactions in leaf-cutting ants is more complex than that seen in most other insects. Leaf-cutting worker ants are grouped into castes, displaying polymorphism and performing different tasks in the colony, which can influence parasitism rates by phorids [34]. Furthermore, leaf-cutting ant larvae present in the nests have a wide range of sizes, which, as seen here, could influence the number of eggs laid in each host.…”

Phorid fly parasitism rates vary between individual colonies of the leaf‐cutting ant Atta laevigata

“…Leaf-cutting ants transiting foraging trails and working in the areas where the leaves are being cut are subject to parasitism by several species of phorid flies (Diptera: Phoridae). These parasitoids oviposit in the head or abdomen of their hosts (Bragança, 2011;Bragança et al, 2016;Farder-Gomes et al, 2018;Souza et al, 2021).…”

“…It has been shown that large worker ants are preferentially attacked by phorid species that are themselves comparatively larger than other phorid species, while smaller workers are more frequently attacked by smaller parasitoids (Bragança et al, 1998;Elizalde & Folgarait, 2011;Farder-Gomes et al, 2018;Tonhasca Jr. et al, 2001). For example, Eibesfeldtphora phorids are relatively large flies that preferentially parasitize the largest A. laevigata and Atta bisphaerica Forel workers, while the smallest workers are parasitized by smaller phorids such as M. grandicornis (Bragança et al, 2021;Souza et al, 2021). Bragança et al (2021) studied four colonies of A. bisphaerica.…”

“…The data used in the present study was obtained during the collections carried out by Souza et al (2021). These authors compared parasitism by phorids between worker ants on trails and on mounds.…”