Foraging activity of Trachymyrmex fuscus (hymenoptera: formicidae) in a degraded area

Two Trachymyrmex fuscus nests were observed between 2001 and 2002 in order to analyze the ant's foraging activity and the substrate collected by workers in an area modified by human activity. The analysis of results demonstrated alterations in the diel activity patterns of workers during the several months studied; however, we could not establish direct relations with variations in temperature and relative humidity. The materials transported to grow the symbiotic fungus were, for the most part, recently fallen or dry leaves, flowers, twigs, and seeds. The distances traveled by the ants until the foraging area and their collected material preferences revealed an opportunistic behavior, in which workers use plant parts according to the vegetation's phenology.

Ghost-ant: Post-embryonic development of the worker caste of Tapinoma melanocephalum (hymenoptera: Formicidae)

This study examines some aspects of the basic biology of the worldwide distributed ant Tapinoma melanocepbalum Fabricius. The number of larval instars and the growth ratio between each instar are given. We used colonies containing only queens and workers, and later removed these queens in order to estimate the production of eggs and the duration of immature development of the worker caste. Measurements of larvae cephalic capsule widths revealed that workers of the ghost-ant have four larval instars from egg-hatching to adult. The mean growth rate for the species is 1.38, in accordance with Dyar's rule. The highest egg production was 5.3±2.2 eggs/day/queen and the analysis of these brood suggested the presence of two kinds of eggs inside the colony. The development of workers from egg to adult lasted 16-52 days with the embryonic development longer than larval, prepupal or pupal stages. Despite the slow egg-laying by queens, our findings also showed that colonies of T. melanocephalum grow faster than colonies of other tramp ants.

Comparative morphology of the midgut of three species of Cephalotes (Hymenoptera, Formicidae, Myrmicinae)

Studies of histological nature, histochemistry and ultra-morphology of the midgut of three species of ants belonging to the genus Cephalotes (atratus, clypeatus and pusillus) were performed. In histology H-E was employed, and in histochemistry techniques for detection of carbohydrates, proteins in general and collagen and calcium fibers were used. The results obtained from this second technique made possible some discussion about the pH of the midgut of these insects. The species are identical in the characters under study. The digestive cells exhibited a secretion that is typical of ants, the apocrine type.

Description and morphometry of the sting apparatus in the three worker casts of Acromyrmex subterraneus brunneus (Formicidae, Attini)

We studied the morphometry of the sting apparatus of Acromyrmex subterraneus brunneus workers by dissection and mounting of the structures on slides, and present here a brief description and illustrations. Sting apparatus examinations showed differences in size, but without morphological differences. The seven morphometric variables studied permitted grouping of the Ac. subterraneus brunneus workers into the following three groups: cluster 1 - consisting of 85, 39 large, 45 medium and 1 small workers; cluster 2 - consisting of 44 small workers, and cluster 3 - consisting of 6 large workers. This study demonstrated that all worker castes follow the same morphological pattern, although functional characteristics of the sting apparatus should be highlighted.

Dispersal of the delayed action insecticide sulfluramid in colonies of the leaf-cutting ant Atta sexdens rubropilosa (Hymenoptera: Formicidae)

Toxic baits are the most used control method for leaf-cutting ants due to their high effectiveness and because they are considered the safest for humans. Taking into account that the importance of leaf-cutting ants as pests, knowing the process by which dispersal and worker contamination is achieved becomes essential to understand several aspects about the functioning of a bait-borne AI (active ingredient) used in toxic baits. It has been established that an effective toxic bait should have a delayed- action AI, but its dispersion among the different sizes of workers is unknown. Workers of different sizes are involved in quite different tasks such foraging, cultivation of symbiotic macrofungus or control of deleterious microfungi. Therefore, we prepared a toxic bait containing the delayed-action AI sulfluramid and a dye (Rhodamine B) as an AI tracer in order to study dispersal and contamination in colonies, evaluated at different periods and in relation to different workers' sizes. Both field and laboratory colonies were evaluated. The great level of contamination, about 50% at 24 hours, in all sizes of workers demonstrates that worker contact with toxic bait is intense within this period. The distribution in field and laboratory colonies was similar. This contamination pattern is probably enough to cause the colony to die because of contamination of smaller workers, leading to the loss of control of the aggressive microfungi, which can quickly overgrow the symbiotic fungus culture. The dispersal dynamics of AI in leaf-cutting ant workers is important for investigations on the mode of action of this insecticide in the colony, and as a reference in future studies, such as those attempting to reduce the concentration of AIs in baits to reduce their environmental impact, or for facilitation of new AI screening.

Isolation and growth of the symbiotic fungus of Atta capiguara (Hymenoptera: Formicidae)

This work's objectives were to isolate and evaluate the growth of the symbiotic fungus of Atta capiguara Gonçalves on artificial medium, under different pH and temperature conditions. Isolation was accomplished using the following media: Sabouraud, oat-agar, PDA, and PDA with the addition of extracts from the grasses Paspalum sp. Flügge and Hyparrhenia rufa (Nees) Stapf.. The medium used in the growth study was PDA with the addition of a Paspalum sp. (0.22%, w/v) extract at initial pH values of 4.5, 6.0, and 7.5. Mycelium disks were transferred to plates containing the culture medium. The plates were maintained at temperatures of 20, 23, and 26 ± 1°C. Mycelial radial growth evaluations were performed at 7, 14, 21, 28, and 35 days of incubation. Fungus isolation was obtained in all media studied. The highest radial means were obtained at initial pH values of 6.0 and 7.5 and temperatures of 23 and 26± 1°C. Greater plot losses occurred at the initial pH condition of 7.5. In general, A. capiguara fungi can be grown in the medium studied, at an initial pH of 6.0 and temperatures of 23 or 26± 1°C. Radial growth evaluations at 14 and 28 days of incubation can be recommended for substrate studies involving the symbiotic fungus.

Microdon tigrinus (Diptera, Syrphidae): Populational fluctuations and specificity to the nest of Acromyrmex coronatus (Hymenoptera: Formicidae)

This study was performed in the southern and southeastern regions of Brazil, visiting numerous municipalities, over a period of 25 years, excavating nests of 12 species of leaf-cutting ants of the Acromyrmex genus. Larvae and pupae of Microdon tigrinus were found only in nests of the leaf-cutting ant Acromyrmex coronatus, indicating high specificity. Observation showed that larvae and pupae were well accepted in the nests and the adults, immediately after puparia eclosion and prior to wing distension, were not attacked by the workers, suggesting that they produce semiochemicals for a short time period until they arrive outside the Acromyrmex coronatus nest. It was postulated that these larvae feed on the organic detritus of the nest, as shown for Microdon larvae of other species.

Thelytokous parthenogenesis in the fungus-gardening ant Mycocepurus smithii (Hymenoptera: Formicidae)

The general prevalence of sexual reproduction over asexual reproduction among organisms testifies to the evolutionary benefits of recombination, such as accelerated adaptation to changing environments and elimination of deleterious mutations. Documented instances of asexual reproduction in groups otherwise dominated by sexual reproduction challenge evolutionary biologists to understand the special circumstances that might confer an advantage to asexual reproductive strategies. Here we report one such instance of asexual reproduction in the ants. We present evidence for obligate thelytoky in the asexual fungus-gardening ant, Mycocepurus smithii, in which queens produce female offspring from unfertilized eggs, workers are sterile, and males appear to be completely absent. Obligate thelytoky is implicated by reproductive physiology of queens, lack of males, absence of mating behavior, and natural history observations. An obligate thelytoky hypothesis is further supported by the absence of evidence indicating sexual reproduction or genetic recombination across the species' extensive distribution range (Mexico-Argentina). Potential conflicting evidence for sexual reproduction in this species derives from three Mycocepurus males reported in the literature, previously regarded as possible males of M. smithii. However, we show here that these specimens represent males of the congeneric species M. obsoletus, and not males of M. smithii. Mycocepurus smithii is unique among ants and among eusocial Hymenoptera, in that males seem to be completely absent and only queens (and not workers) produce diploid offspring via thelytoky. Because colonies consisting only of females can be propagated consecutively in the laboratory, M. smithii could be an adequate study organism a) to test hypotheses of the population-genetic advantages and disadvantages of asexual reproduction in a social organism and b) inform kin conflict theory. For a Portuguese translation of the abstract, please see Abstract S1. © 2009 Rabeling et al.

Toxicological and histopathological effects of boric acid on atta sexdens rubropilosa (Hymenoptera: Formicidae) workers

The current study compared the toxicity of different concentrations of boric acid in adult workers of Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae), with toxicological bioassays, and examining the dose-dependent and time-dependent histopathological changes, of the midgut, Malpighian tubules, and postpharyngeal glands. Our results revealed the importance of conducting toxicological bioassays combined with morphological analyses of the organs of ants chronically exposed to insecticides used in commercial ant baits. In vitro bioassays showed that boric acid significantly decreases the survivorship of workers regardless of concentration, whereas the morphological data suggested progressive dose-dependent and time-dependent changes in the organs examined, which were evident in the midgut. The midgut is the first organ to be affected, followed by the postpharyngeal gland and Malpighian tubules. This sequence is in agreement with the absorption pathway of this chemical compound in the midgut, its transference to the hemolymph, possibly reaching the postpharyngeal glands, and excretion by the Malpighian tubules. These progressive changes might be due to the cumulative and delayed effect of boric acid. Our findings provide important information for the understanding of the action of boric acid in ant baits in direct and indirect target organs. © 2010 Entomological Society of America.

Ant diversity in a sugarcane culture without the use of straw burning in southeast, são paulo, Brazil

Problem statement: One of the current requirements of agroecosystem management is the maintenance of biodiversity. Manual sugarcane harvesting with the previous burning of straw has been gradually replaced by mechanical harvesting in Brazil. However, the diversity of Formicidae, which can be a natural pest controller, has not been studied in this new system yet. Approach: This study was carried out to assess the diversity of ants in an exclusively mechanically harvested sugarcane culture based on the hypothesis that species richness and abundance will increase with the deposition of straw in this culture system. Ants were sampled using pitfall traps in six sugarcane cultivars during three consecutive harvest cycles. Results: A total of 8,139 ants, distributed in 39 species, were collected. Richness, abundance and diversity differed between harvest cycles, especially in the first cycle, when the soil did not have any straw and in the two last cycles and the straw layer was about 10-15 cm thick. The communities found in the second and third cycles were similar and the maintenance of straw in the culture contributed to a greater species diversity, particularly of generalist predaceous taxa, which may contribute to the natural control of pests. Conclusion: The diversity of ants increased with straw deposition, including of taxa that may be beneficial to the sugarcane culture. However, new studies of the predatory and competition relations in this agroecosystem are necessary. © 2010 Science Publications.

Chemometric analysis of Hymenoptera toxins and defensins: A model for predicting the biological activity of novel peptides from venoms and hemolymph

When searching for prospective novel peptides, it is difficult to determine the biological activity of a peptide based only on its sequence. The trial and error approach is generally laborious, expensive and time consuming due to the large number of different experimental setups required to cover a reasonable number of biological assays. To simulate a virtual model for Hymenoptera insects, 166 peptides were selected from the venoms and hemolymphs of wasps, bees and ants and applied to a mathematical model of multivariate analysis, with nine different chemometric components: GRAVY, aliphaticity index, number of disulfide bonds, total residues, net charge, pI value, Boman index, percentage of alpha helix, and flexibility prediction. Principal component analysis (PCA) with non-linear iterative projections by alternating least-squares (NIPALS) algorithm was performed, without including any information about the biological activity of the peptides. This analysis permitted the grouping of peptides in a way that strongly correlated to the biological function of the peptides. Six different groupings were observed, which seemed to correspond to the following groups: chemotactic peptides, mastoparans, tachykinins, kinins, antibiotic peptides, and a group of long peptides with one or two disulfide bonds and with biological activities that are not yet clearly defined. The partial overlap between the mastoparans group and the chemotactic peptides, tachykinins, kinins and antibiotic peptides in the PCA score plot may be used to explain the frequent reports in the literature about the multifunctionality of some of these peptides. The mathematical model used in the present investigation can be used to predict the biological activities of novel peptides in this system, and it may also be easily applied to other biological systems. © 2011 Elsevier Inc.

Presence and distribution of the endosymbiont Wolbachia among Solenopsis spp. (Hymenoptera: Formicidae) from Brazil and its evolutionary history

Wolbachia are intracellular bacteria that commonly infect arthropods. Its prevalence among ants of the genus Solenopsis is high. In the present study, the presence and distribution of these endosymbionts was examined among populations of Solenopsis spp. from Brazil. A phylogenetic analysis based on the wsp gene was conducted to infer the evolutionary history of Wolbachia infections within the populations surveyed. A high frequency of Wolbachia bacteria was observed among the genus Solenopsis, 51% of the colonies examined were infected. Incidence was higher in populations from southern Brazil. However, little genetic variability was found among different Wolbachia strains within supergroups A and B. Our findings also suggest that horizontal transmission events can occur through the social parasite S. daguerrei. © 2012 Elsevier Inc..

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.

Compared morphology of the immatures of males of two urban ant species of camponotus

The immatures of males of two species of Camponotus ants (Hymenoptera: Formicidae) are described and compared by light and electron microscopy. The numbers of larval instars were determined: Camponotus rufipes Fabricius (Hymenoptera: Formicidae) have four instars; and Camponotus vittatus Forel have three. Male larvae of the two species are similar to previously described Camponotus larvae, sharing the following traits: basic shape of body and mandible, presence of 'chiloscleres', 'praesaepium' (some specimens), labial pseudopalps, and ten pairs of spiracles. However, larvae of the two species can be separated by bodily dimensions and based on their hair number and types. Worker larvae of C. vittatus previously described are extensively similar to male larvae, with only a few inconspicuous differences that may result from intraspecific variation or sexual differences.

Queen lipid content and nest growth in the leaf cutting ant (Atta sexdens rubropilosa) (Hymenoptera: Formicidae)

The relationship between the queens' lipid content and nest growth (population size, biomass and nest architecture) was studied from founding up to 1 year. Nests aged 3, 4, 5, 6, 9 and 12 months were dug in the field, and their dimensions were measured. The ant nest population and fungus garden was also collected. The sample was taken to the laboratory where we counted the worker population and weighed the biomass (fungus plus offspring) and queens. Queens were separated for the determination of lipids. The lipid content in the bodies of queens decreased in the first months, then stabilized (at 4-6 months) before increasing in months 9 and 12. Nest biomass (symbiotic fungus and offspring) and worker population increased over time. The structural growth of the nests was observed by excavating around them. Initially nests (3 months old) had one chamber at an average depth of 15 cm. By 1 year, the nests had three or four deep chambers, and were about 3-4 m deep. Our study contributes to knowledge of the dynamics of the energy-reserve expenditure by queens during colony founding and colony development for up to 1 year. © 2013 Copyright Taylor and Francis Group, LLC.