Comparative immature morphology of Brazilian fire ants (Hymenoptera: Formicidae: Solenopsis)

Although common in Brazil, the biology of the fire ant Solenopsis saevissima (Smith) is still poorly studied. Larval descriptions are useful to genus-level ant systematics and sometimes to species-level taxonomy. This study presents a detailed description of juveniles of S. saevissima from Brazil, which were compared with Brazilian specimens of Solenopsis invicta Buren, Solenopsis geminata (Fabricius), and Solenopsis altipunctata Pitts. Different larval instars were separated by diagnostic morphological traits which were confirmed by observing moults. Reproductive larvae could be easily sorted by their distinctive body dimensions and shape. Contrary to previous reports on this species, the larvae of S. saevissima proved to be generally identical to those of S. invicta, while a few specimens resembled those of other close species, such as Solenopsis megergates Trager. Mature larvae thus presented considerable intraspecific variation in some characters recently proposed to aid fire ant species separation (morphology of head hairs). © 2012 Eduardo Gonalves Paterson Fox et al.

Intraspecific and intracolonial variation in the profile of venom alkaloids and cuticular hydrocarbons of the fire ant Solenopsis saevissima smith (Hymenoptera: Formicidae)

Fire ants are aggressive Neotropical ants that are extensively similar in general biology and morphology, making species identification difficult. Some fire ant species are top-rated pests spreading throughout the world by trade vessels. Many researchers attempted to sort between invasive and native species by using chemical characters, including patterns of venom alkaloids. The present study is the first to report intraspecific variation in some chemical characters, namely, cuticular hydrocarbons and venom alkaloids, within the Brazilian fire ant species Solenopsis saevissima and also reports on within-nest variations among members of different castes. Two different haplotypes (cryptic species) of S. saevissima were clearly identified, one presenting a predominant combination of the venom alkaloids cis- and trans-2-methyl-6-undecylpiperidine with the cuticular hydrocarbons C23, 3-Me-C23, 10-C 25:1, C25, and 3-Me-C25, and the other a predominant combination of cis- and trans-2-methyl-6-tridecenylpiperidine with predominance of 12-C25:1, C25, 11-Me-C25, 3-Me-C25, 13-C27:1, C27, and 13-Me-C 27. Intranest variations revealed that the proportions among these compounds varied sensibly among workers of different sizes, gynes, and males (no alkaloids were detected in the latter). Larva contained vestiges of the same compounds. The recorded chemical profiles are quite different from previous reports with S. saevissima samples from So Paulo. The finds thus support other recent claims that S. saevissima includes cryptic species; the study, moreover, adds the find that they can occur in the same geographical location. © 2012 Eduardo Gonalves Paterson Fox et al.

HOST-SPECIFICITY OF SEVERAL PSEUDACTEON (DIPTERA, PHORIDAE) PARASITES OF FIRE ANTS (HYMENOPTERA, FORMICIDAE) IN SOUTH-AMERICA

We tested the host specificity of several parasitic Pseudacteon scuttle flies in South America with 23 species of ants in 13 genera. None of these ant species attracted Pseudacteon parasites except Solenopsis saevissima (F. Smith) and to a lesser extent Solenopsis geminata (Fab.). This result is encouraging because it indicates that the Pseudacteon flies tested in this study would not pose an ecological danger to other ant genera if these flies were introduced into the United States as classical biological control agents of imported fire ants. This prediction of host specificity will, of course, need to be validated with potential hosts in the United States before these flies can be released.

Resource partitioning among epigaeic and hypogaeic ants (Hymenoptera: Formicidae) of a Brazilian cocoa plantation

Patterns of dietary and foraging strata utilization by the ground ant community of a Brazilian cocoa planatation were examined using sugar, meat and flour baits on the surface as well as buried. A total of 49 ant species was recorded, including 10 species of Pheidole. Strong dominance was exercised by Solenopsis geminata at both surface and subterranean strata, and at all food resources. The dissimilarity matrix of the epigaeic ant fauna was much greater than that for the hypogaeic species. At least four guilds were identified: the fungus-growing ants, epigaeic nectivores, epigaeic carnivores, and hypogaeic foragers. Niche breadth reduction, leading to the formation of guilds, permits the coexistence of many species in the this ground ant community from a tropical cocoa plantation. -Authors

Morphological Notes on the Worker and Queen Larvae of the Thief Ant Solenopsis helena (Hymenoptera, Formicidae, Myrmicinae) from Brazil

Young and mature larvae of queen and workers of the thief ant, Solenopsis helena, are herein described for the first time. Specimens were treated and described by usual methods of light and scanning electron microscopy. Many of the observed characteristics confirmed traits of the thief ant larva, reinforcing the assumption that they are a distinct group from fire ants. The larva of S. helena can be recognized from other close species by details of the mouthparts, but seem extensively similar to Solenopsis molesta. These findings are useful for taxonomic studies and phylogenetic inferences.

Pustular dermatosis caused by fire ant (Solenopsis invicta) stings in a dog

This paper reports a case of spontaneous fire ant sting dermatitis in canine. The skin lesions consisted of nonfollicular, grouped pustules in the abdominal region. Several fire ants were found attached to the lesional skin. Histopathological findings included an intraepidermal neutrophilic pustule and predominantly neutrophilic interstitial dermatitis. An extensive area of collagen degeneration was also observed below the epidermal pustule. These clinical and histopathological findings are remarkable similar to those observed in fire ant stings in humans.

General morphology and ultrastructure of the venom apparatus and convoluted gland of the fire ant, Solenopsis saevissima

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Proteomic View of the Venom from the Fire Ant Solenopsis invicta Buren

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Manipulation of fire ant density, Solenopsis spp., for short-term reduction of Diatraea saccharalis larval densities in Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Functional ultrastructure of the midgut of the fire ant Solenopsis saevissima Forel 1904 (Formicidae : Myrmicinae)

Solenopsis saevissima has a midgut composed of columnar, regenerative, and goblet cells. The midgut epithelium was covered by a basal lamina. Outside the basal lamina, layers of inner oblique, circular, and outer longitudinal muscles were present. Columnar cells showed a basal plasma membrane containing numerous folds, mitochondria, and the nucleus. Rough endoplasmic reticulum, Golgi bodies, membrane bounded vacuoles, and spherocrystals were found in this region. The apical plasma membrane was constituted by microvilli, which were above a region rich in mitochondria. Regenerative cells were found in groups lying by the basal lamina. Goblet cells were associated with an ion-transporting mechanism between the haemolymph and the midgut epithelium. These cells were lying by the midgut lumen and large microvilli were evident, but the cytoplasmic features were similar to the columnar cells.

Rearing of Pseudacteon spp (Dipt, Phoridae), parasitoids of fire ants (Solenopsis spp) (Hym, Formicidae)

After exposure of Solenopsis saevissima colonies maintained in plastic trays to phorid attack in the field, and subsequent transfer of colonies to covered plastic buckets, we confirmed that P. wasmanni and P. litoralis are indeed parasitoids of fire ant workers. The period from attack to emergence of phorid adults ranged from 35 to 46 days. Adult phorids were maintained live in glass vials with sugar water as a food source for 5 days. These results indicate that Pseudaceton can be reared for biological control release programs with minimal difficulty. Furthermore, parasitized workers could be easily transferred from South America to quarantine laboratories within the egg to adult emergence time period.

EXPERIMENTAL INCIPIENT NEST TRANSPLANTS AND SURVIVORSHIP OF SOLENOPSIS-INVICTA BUREN (HYM, FORMICIDAE) IN BRAZIL

Transplants of incipient colonies of the fire ant, Solenopsis invicta into areas in which mature colonies had been eliminated did not result in higher rates of success than in areas in which mature colonies were present. However for both types of sites, Pogonomyrmex (Ephebomyrmex) nagelli colonies were found in cleared sites used for transplants, with the number of translocated P. nagelli nests higher in areas which had not been treated with Mirex for S. invicta colony reduction. These results suggest that small colonies may be displaced by larger colonies of other species.

SOLENOPSIS (HYMENOPTERA, FORMICIDAE) FIRE ANT REACTIONS TO ATTACKS OF PSEUDACTERON FLIES (DIPTERA, PHORIDAE) IN SOUTHEASTERN BRAZIL

We studied the responses of Solenopsis fire ants to Pseudacteon phorid fly attacks in southeastern Brazil. The presence of these phorid parasites triggered a suite of phorid-specific defense responses including reduced foraging, bait guarding, a curled defensive posture, and general colony immobility. The existence of these phorid-specific defenses indicates that Pseudacteon phorids exert substantial evolutionary pressure on South American fire ant populations.