Trajectory of Water- and Fat-Soluble Dyes in the Grass-Cutting ant Atta capiguara (Hymenoptera, Formicidae): Evaluation of Infrabuccal Cavity, Post-Pharyngeal Glands and Gaster

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Occurrence of different gynandromorphs and ergatandromorphs in laboratory colonies of the urban ant, Monomorium floricola

Colonies of Monomorium floricola (Jerdon) in laboratory conditions showed gynandromorphic and ergatandromorphic specimens, the former with nine different combinations of male and female tissues and the latter with 6 different combinations. Their development from egg to adult was around 74.6 days for gynandromorphs, and 87.5 days for ergantandromorphs.

Toucans ( Ramphastidae) and hornbills ( Bucerotidae) as ant followers.

Toucans, especially species of the group Ramphastos vitellinus, occasionally follow armies of ants in tropical forests, on the look out for prey disturbed by the ants. Two methods of searching are used: examining the ground or the lianas and trunks. In contrasts, forest hornbills, (white crested hornbill Tropicranus albocristatus), frequently follow ant armies in Africa. After waiting poised in an erect position, they leap forward towards the ground or at the trunk, sometimes reaching up into the leaves.-translated by C.Wilson

Heritability of the number of ovarioles in honey bee workers (Apis mellifera L.) (hym.:apidae)

Narrow and broad sense heritabilities (h2) of the number of ovarioles in Apis mellifera L. workers were estimated using two distinct data sets, based on groups of half (queens inseminated by several drones) and super-sisters (single drone insemination). The values found are in the usual range for economically important characters (0.25-0.38).

Cellulose degradation by Leucocoprinus gongylophorus, the fungus cultured by the leaf-cutting ant Atta sexdens rubropilosa

Leucocoprinus gongylophorus, the fungus cultured by the leaf-cutting ant Atta sexdens rubropilosa, is able to degrade efficiently cellulose, microcrystaline cellulose, carboximethylcellulose, and cellobiose. Analysis of the degradation products indicate that the fungus produce extracellular β-glucosidase, exo- and endo-glucanase. The importance of cellulose degradation to the association of fungus and ant is discussed.

Geographic variation of Africanized honey bees (Apis mellifera L.) in Brazil: Multivariate morphometrics and racial admixture

The correspondence between morphometric and isozymic geographic variation patterns of Africanized honey bees in Brazil was analyzed. Morphometric data consisted of mean vectors of 19 wing traits measured in 42 local populations distributed throughout the country. Isozymic data refer to allelic frequencies of malate dehydrogenase (MDH), and were obtained from Lobo and Krieger. The two data sets were analyzed through canonical trend surface, principal components and spatial autocorrelation analyses, and showed north-south dines, demonstrating that Africanized honey bees in southern and southeastern Brazil are more similar to European honey bees than those found in northern and northeastern regions. Also, the morphometric variation is within the limits established by the racial admixture model, considering the expected values of Africanized honey bee fore wing length (WL) in southern and northeastern regions of Brazil, estimated by combining average values of WL in the three main subspecies involved in the Africanization process (Apis mellifera scutellata, A. m. ligustica and A. m. mellifera) with racial admixture coefficients.

Morphological prediction of worker size discrimination and relative abundance of sympartic species of Pseudacteon (Dipt., Phoridae) parasitoids of the fire ant, Solenopsis saevissima (Hym., Formicidae) in Brazil

Patterns of attack for collected species of phorids are predicted using multivariate morphometrics of female Pseudacteon species and worker size distributions of parasitized fire ants, Solenopsis saevissima. The model assumes that there is a direct correlation between phorid size and the size range of the worker ant attacked, and presumes that worker sizes are a resource that is divided by sympatric phorid species to minimize joint parasitism. These results suggest that the community of sympatric Pseudacteon species on only one host species coexists by restricting the size of workers attacked, and secondarily by differing diel patterns of ovipositional activity. When we compared relative abundance of species of Pseudacteon with the size distribution of foragers of S. saevissima, our observed distribution did not differ significantly from our predicted relative abundance of females of Pseudacteon. The activity of Pseudacteon may be a factor determining forager size distributions.

Effect of constituents of the foliar wax of Didymopanax vinosum on the foraging activity of the leaf-cutting ant Atta sexdens rubropilosa

Leaf epicuticular waxes may affect substrate selection by leaf-cutting ants, and host recognition by several phytophagous insects. The influence of the crude epicuticular wax of Didymopanax vinosum E. March. (Araliaceae), and its major constituents lupeol and free primary alcohols, on substrate selection by the leaf-cutting ant Atta sexdens rubropilosa Forel, was investigated. Two ant colonies were used in laboratory bioassays. Corn flakes (zea) were impregnated with chloroform solutions of the substances being tested and fed to the adults. One of the colonies gave results, in most of the tests, not significantly different from the controls. The other colony, however, discriminated against the crude wax, a strong deterrent effect being observed from the first of a series of eight trials. The same colony was able to discriminate against lupeol after the second trial. The fraction of primary n-alcohols (22% C28, 66% C30 and 12% C32) deterred feeding only after the fifth trial. The results demonstrate that some constituents of epicuticular waxes may deter the foraging activity of A. sexdens rubropilosa, depending, however, on the colony under observation. It is suggested that lupeol, of the foliar wax of D. vinosum, is an important deterrent to leaf-cutting ants, although with less pronounced effects than those observed in tests with the crude wax.

Honey Ants (Genus Myrmecocystus) Macroecology: Effect of Spatial Patterns on the Relationship between Worker Body Size and Geographic Range Size

Macroecology evaluates the partitioning of physical space and resources among organisms through correlation among ecological variables, such as geographical range size and shape, body size, and population density, measured at large geographical and taxonomic scales. In this article, we analyzed the spatial patterns in worker body size and geographic range size for the 27 described species of honey ants, genus Myrmecocystus Wesmael, in the United States and Mexico, and especially the relationship between these 2 variables after statistically removing their spatial patterns. The 2 variables are correlated, but also displayed significant spatial patterns, as detected by trend surface and spatial autocorrelation analyses. After removing these spatial effects, worker body size and geographic range size were still positively correlated. The relationship, therefore, is not a consequence of spatial effects and it does follow Brown's model, which predicts that the geographic range size will have a positive slope on body size. In this model, the lower population densities caused by foraging activities and local territorial competition are associated with a large geographic range, avoiding stochastic extinction. Although this constraint in local population density does not necessarily hold for small organisms such as insects that could achieve high densities even in very small areas and patchy habitats, it may hold for social insects, especially ants, because of the local competition among colonies.

Study of the presence of the spores of Clostridium botulinum in honey in Brazil

The isolation of Clostridium botulinum from honey samples is described. Botulism is characterized as an intoxication provoked by ingestion of contaminated foods with this toxin. Infant botulism happens by the ingestion of spores of C. botulinum together with food that in special conditions of the intestinal tract, such as those present in babies of less than 1 year old, will allow the germination and colonization of the intestine with production and absorption of botulinic toxin. The samples were subjected to dilution and to a thermal shock and cultivated in modified CMM (Difco). Cultures were subjected to Gram smears and toxicity tests in mice. The toxic cultures were purified in RFCA (Oxoid) plates and incubated in anaerobic jars. Positive samples were typed using the mouse assay neutralization test. From the 85 honey samples analyzed, six were positive for C. botulinum (7.06%), and identified as producers of type A, B, and D toxins.

Hypogaeic anti epigaeic ant (Hymenoptera: Formicidae) assemblages of atlantic costal rainforest and dry mature and secondary amazon forest in Brazil: Continuums or communities

Meat, flour and sugar baits were used on the soil surface and buried to examine species composition of the ant fauna in three separate tropical forests in Brazil, and to control for the effect of the regional faunal pool. Compositional mosaic diversities were comparable among areas, bait types and foraging strata. Mosaic diversity was independent of mean assemblage size. The number of unique species per sampling unit was correlated with mean assemblage size. Canonical correspondence analysis ordered species first by foraging substrate, second by geographic location, and third by diet. The first axis was significantly correlated with mean similarity and affinity. Mean Mahanalobis distances between centroids of groups based upon foraging strata were significantly larger than between localities, indicating local ecological pressures stronger than regional species pool constraints. As most. species foraged in only one stratum in one geographical position and were not omnivorous, the response of species to environmental gradients (continuums) showed a lower coherency with these patterns than did communities, structured around guilds based upon foraging strata and diet.

Ant exclusion and reproduction of Croton sarcopetalus (Euphorbiaceae)

A total of 20 insect species were observed on the extrafloral nectaries (EFNs) of Croton sarcopetalus. The most frequent ant species were Zacryptocerus sp., Crematogaster brevispinosa, C. scelerata, and Linepithema humile. Ants continuously patrolled the plants taking extrafloral nectar. Experimental data showed that there were no significant differences in either the degree of herbivory or in the reproductive output between control stems (with ants) and treated ones (without ants). We found no significant evidence of protection by ants mediated by EFNs in C. sarcopetalus. It is possible that the plant has other mechanisms than ant protection to prevent herbivore damage (e.g., hairs, latex, chemical defense). As this species occupies the southernmost distribution for the genus, the presence of EFNs in this species may be the remnant of a mutualistic interaction with the ants in tropical regions, where the abundance and diversity of ants and herbivores are comparatively higher. To draw accurate patterns in the genus Croton, further investigations in other species from tropical regions of South America are needed.

Nest architecture and population dynamics of the ponerine ant Ectatomma edentatum (Hymenoptera, Formicidae)

Twelve nests of Ectatomma edentatum (Hymenoptera, Formicidae) were collected from January to December 1996, in Rio Claro, SP, southeastern Brazil. This species excavates their nests up to 1, 10m deep, containing 2, 3, or 4 chambers with an entrance hole of up to 5mm diameter. Colonies with 104, 79, and 82 adult ants respectively were found in February, October, and November. These numbers decreased from March. Colonies with 21 and 16 adult ants were observed in May and July. The colonies' populations increased again in August. Immature stages were not seen January, February, and July, but there were many between March-April and September-November. There was no significant correlation between the number of individuals per colony and temperature or between the number of colonies and relative humidity and rainfall.

Number of larval instars of the ant Pachycondyla (=Neoponera) villosa (Formicidae: Ponerinae) determined by the rule of Dyar

In this work we present the number of larval instars in the Ponerinae ant Pachycondyla (=Neoponera) villosa. The analysis of maximal head capsule width measurement of 147 larvae was made. Four larval instars were measured: 1st instar the cephalic capsule varied from 0.18mm to 0.22mm; 2nd instar from 0.23mm to 0.27mm; 3rd instar from 0.30mm to 0.33mm and the 4th instar varied from 0.35mm to 0.38mm. The mean growth rate was 1.2375 according to the rule of Dyar. We also reviewed the number of larval instars for 35 ant species.

The occurrence and foraging behavior of the army ant Eciton vagans dubitatum in the Itirapina area, São Paulo State, Brazil (Hymenoptera, Formicidae)

This paper discusses the occurrence of the army ant Eciton vagans dubitatum in a semi-deciduous forest, Itirapina area, São Paulo State, Brazil. Comparisons of bivouac and raiding pattern are done in relation to other subspecies of Eciton vagans.