Ant Parasitoids Research Articles

Visual and chemical cues used in host location and acceptance by a dipteran parasitoid.

Locating potential hosts for egg laying is a critical challenge in the life history of many insects. Female insects in several orders have evolved mechanisms to find hosts by using olfactory and visual signals derived from their hosts. We describe visual and chemical cues used by the dipteran parasitoid Apocephalus paraponerae (Diptera: Phoridae) in the location and acceptance of its host ant Paraponera clavata (Hymenoptera: Formicidae: Ponerinae). Our results show that A. paraponerae uses the visual cue of ant body size when locating hosts at short range and that these flies lay more eggs in ants that retain their surface chemicals than in ants with these chemicals removed. We compare the cues used by A. paraponerae with cues used by tephritid fruit flies in location and acceptance of their hosts, and we suggest further avenues for the study of host location, acceptance, and host discrimination of A. paraponerae and other parasitoids of ants.

Parasitoid–host relationships when host size varies: the case of Pseudacteon flies and Solenopsis fire ants

Abstract.1. Phorid flies in the genus Pseudacteon are parasitoids of ants. Variation in host size preferences of four South American and two North American Pseudacteon species on monogyne and polygyne forms of their host Solenopsis species [S. invicta Buren and S. geminata (F.), respectively] was documented.2. Monogyne Solenopsis workers were, on average, significantly larger than polygyne workers, and the average size monogyne worker attacked was significantly larger than the average size polygyne worker attacked in four of the six Pseudacteon species.3. Three South American Pseudacteon species attacked larger than average size workers, whereas one attacked smaller than average size workers, in both monogyne and polygyne forms. Both North American Pseudacteon species attacked larger than average size polygyne workers and smaller than average size monogyne workers.4. Three Pseudacteon species were reared from eggs to adults in infected ants in the laboratory. The size of the emergent phorid fly was related positively to the size of the host worker ant, with females emerging from larger hosts. Similar patterns were documented for both monogyne and polygyne forms.5. The mean size of worker host from which phorids emerged did not differ significantly between the monogyne and polygyne forms in the subsample of phorids reared to adults.6. The observed patterns elucidate factors that may cause variation in Pseudacteon sex ratios, and have implications for biological control efforts of pest Solenopsis species.

Foraging ecology and patterns of diversification in dipteran parasitoids of fire ants in south Brazil

1. At least sixteen species of parasitoid flies in the genus Pseudacteon (family Phoridae) attack fire ants in the Solenopsis saevissima subcomplex in South America. Little is known of behavioural or ecological differences among Pseudacteon parasitoids of fire ants, although their coexistence in multispecies communities would suggest that important differences exist. Seven Pseudacteon species in two separate communities were studied in south‐east Brazil. The way in which hosts detect and respond to the presence of parasitoids, attack rates of the parasitoids, and host location behaviour of the parasitoids were examined.2. Reductions in fire ant recruitment were more closely related to the number of ants attacked along a foraging trail than to the amount of time that a phorid was present.3. Pseudacteon solenopsidis differed from other phorid species by flying backwards while pursuing ants, by attacking at lower rates than other phorids, and by spending longer around fire ant foraging trails than other phorids before departing. Fire ant recruitment to food often rebounded in the continued presence of P. solenopsidis.4. In each of the two communities, certain Pseudacteon species appeared frequently at Solenopsis foraging trails, whereas others appeared predominantly at mound disturbances. Two distinct size classes of phorids were present in each community, and the community with the larger ant host species also had a third and larger phorid species. No phorid species from the same community had similar body sizes and similar host location behaviours, although numerous species from different communities shared both of these traits.5. Heterogeneity in host size and in the ecological circumstances under which hosts are vulnerable to attack appears to have influenced the evolution and perhaps maintenance of diverse Pseudacteon communities.

Specialized parasitoid attracted to a pheromone of ants

Apocephalus paraponerae(Diptera: Phoridae) parasitizes workers of the giant tropical ant, Paraponera clavata(Hymenoptera: Formicidae), in Central America. When female parasitoids locate fighting or injured workers of this species, they deposit one or more eggs in them and feed from wounds. Male parasitoids are also attracted to hosts for feeding and to locate females for mating. In a series of experiments it was demonstrated that males and females of this parasitoid were attracted to two products of the mandibular glands of P. clavata , 4-methyl-3-heptanone and 4-methyl-3-heptanol. These compounds are produced in the mandibular glands of numerous ant species and serve as alarm pheromones in some species. Phorid parasitoids of ants may routinely use host-produced pheromones to locate hosts, and behavioural interactions between ants and their parasitoids may have shaped the use of these pheromone systems by both interactants.