Search

The presence of antimicrobial-resistant bacteria and carried by ants isolated from hospitals was investigated in Campos dos Goytacazes, RJ, Brazil. Three health institutions were visited from 2001 to 2002 and samples were collected within critical areas of medical care based on criteria of greater risk of patient hospital acquired-infection. Four ant species were identified, Tapinoma melanocephalum (Fabricius)(63.1%), Paratrechina longicornis (Latreille)(21.1%), Monomorium pharaonis (L.)(10.5%), and Solenopsis saevissima (S. Smith)(5.3%) carrying 21 species of bacteria. The tests for bacteria species identification and antimicrobial-resistance profile were carried out by using standardized kits and evaluated by automated equipment. Among the bacteria isolates, some were considered multiresistant isolates, including genera Acinetobacter, Streptococcus, Gemella, and Klebsiella. For Enterobacter antibacterial analysis the disk diffusion standard method was used. The results suggest that there are risks for patients which seek for health assistance in the hospitals studied, and the presence of emerging bacteria isolates in hospital carried by ants must be considered.

The Brazilian Atlantic Forest is one of the world's ‘hot spots’ for conservation because of its high level of endemism and number of endangered species (Myers et al. 2000). After centuries of deforestation, most of the remaining Atlantic Forest is scattered as small fragments on private land (Fonseca 1985, Jorge & Garcia 1997). Pollination could be impaired in these fragments because isolation often negatively influences the dispersal of insects, the most important pollinating agents in the tropics.

Euglossine bees (Hymenoptera: Apidae: Euglossini) are considered keystone species in the neotropics because of their role as pollinators of several plant species, particularly orchids (Dodson et al.1969, Roubik 1992). Pollination by male euglossine bees occurs when they visit flowers to collect fragrances, which may be used for courtship (Eltz et al. 1999) or attraction of other males and females (Peruquetti 2000). Synthetic products that mimic those fragrances have been used frequently in studies of euglossine bee ecology and population structure (Armbruster & McCormick 1990, Powell & Powell 1987, Roubik & Ackerman 1987). The ability of euglossine bees to disperse and find isolated flowers and distant baits (Dressler 1968, Janzen 1971) has led Janzen (1981) and Janzen et al. (1982) to suggest that bees attracted to fragrances come from a wide area that may include different habitats. According to this hypothesis, individuals collected at baiting stations are part of the same pool of bees. However, Armbruster (1993) found significant variation in the number of bees collected at nearby baiting stations, and he considered these differences as demonstration of within-habitat heterogeneity of the euglossine bee community. In Armbruster's model, results of bait collections are strongly affected by the concentration of resources in ‘hot spots’, therefore a sampling station would not necessarily represent the habitat, but only particular microhabitats.

The parasitic phorid Myrmosicarius grandicornis Borgmeier is commonly found around nest entrances of the leaf-cutting ant Atta sexdens (L.) in Brazil, but there is no information about the importance of this fly for A. sexdens. We evaluated the parasitic capability of female M. grandicornis collected in the field and released in laboratory nests of A. sexdens and compared ants' foraging rhythm before and after M. grandicornis were released. We also determined biological characteristics of the parasitoid. Presence of M. grandicornis elicited foragers to abandon their loads and return to the nest, an effect previously described for the phorid Neodohrniphora sp., which is a more abundant A. sexdens parasitoid. Both phorid species occur at the same foraging trails during part of the year and attack ants of different size classes. Therefore, they may have a combined effect on the reduction of A. sexdens foraging. Myrmosicarius grandicornis pupariated inside hosts' head capsules, which are detached from their bodies and deposited in the nest's refuse pile. Adults emerged through the hosts' mouth cavity about a month after oviposition. The characteristics of M. grandicornis biology suggest that this parasitoid completes its development inside A. sexdens nests.

Atta laevigata (Smith) (Hymenoptera: Formicidae) foragers collected in the field and parasitized by Apocephalus attophilus Borgmeier (Diptera: Phoridae) (1.2% of sampled ants) were larger and had lower survival rates than similar non-parasitized foragers. Moreover, the size of parasitized ants was significantly correlated with the number of A. attophilus puparia and percentage of adult emergence. These results suggest that host size is important for the reproductive success of A. attophilus. Different from most ant-parasitizing phorids, A. attophilus exhibits a pre-oviposition behavior that involves walking towards the host and inspecting it, and this careful approach may be responsible for a relatively low percentage of parasitoid detection by A. laevigata. When an exotic resource (Acalypha sp. leaves) was placed on ants' foraging trails, more foragers were recruited, which resulted in the attraction of A. attophilus. The number and recruiting rates of small workers (minima) were significantly higher on leaves visited by A. attophilus, but larger foragers showed no response to phorids. These results demonstrated that minima react to the presence of A. attophilus and suggest a defensive role of these ants against phorid parasitism.

Females of the parasitic phorid Neodohrniphora sp. were collected in the field and released singly inside an observation chamber placed between a laboratory colony of Atta sexdens (L.) and its foraging arena. The number and speed of loaded and unloaded ants returning to the nest, the weight of foragers and their loads, the number of leaf fragments abandoned by ants, and the number of small workers 'hitchhiking' on leaf fragments were measured before phorids were released, while they were in the observation chamber, and after they were removed. Relatively few ants were attacked by Neodohrniphora sp., but the presence of flies prompted outbound ants to return to the nest and caused a significant reduction on the number and mass of foragers. Additionally, the weight of leaf fragments transported by ants was reduced and the number of abandoned fragments increased in response to Neodohrniphora sp. Presence of the parasitoid caused no significant changes in the number of hitchhiking ants. The regular ants' traffic was resumed after phorids were removed, but foraging activity remained below normal for up to three hours. In the field A. sexdens forages mostly at night, but colonies undergo periods of diurnal foraging during which ants are subject to parasitism from several species of phorid flies. Considering that daytime foraging may be necessary for nutritional or metabolical needs, phorids may have a significant impact on their hosts by altering their foraging behavior regardless of the numerical values of parasitism.

Three sampling techniques (yellow sticky trap, visual [Leafturn], and modified vacuum [Handvac]) were compared over a 2-yr period to determine sampling reliability for estimating adult sweet potato whitefly, Bemisia tabaci (Gennadius), population levels in cantaloupes, Cucumis melo L. In experimental plots, the 3 sampling methods indicated similar whitefly population trends throughout the season, and all methods were highly correlated with immature densities. There was a strong correlation of Leafturn samples with Handvac and sticky trap counts. In commercial fields, however, seasonal patterns of population levels detected with sticky traps differed from those detected with the other sampling methods. Adult counts from the Leafturn procedure were more closely correlated with counts from Handvac samples than with those from sticky traps. Estimates of adult abundance measured by Leafturn counts also provided a higher correlation with immature densities than the other methods. In general, estimates of whitefly population trends measured with the Leafturn and Handvac methods were similar in commercial fields despite differences in cultivar planted, year of the test, and insecticide use patterns. Estimates of relative sampling variation (precision) indicated that sticky traps were more efficient in some cases, but, overall, precision did not differ among the sample methods. The relative net precision for adults was greater with the Leafturn and Handvac methods, which were less time consuming than the sticky trap. Comparison of sampling methods in small-plot chemical trials indicated that yellow sticky traps were not reliable for estimating treatment differences. Only the Leaftum and Handvac methods detected significant differences in adult numbers between treated and untreated plots after insecticide applications.

Phoridae flies parasitize several ant species, including many Atta leaf-cutting ants. In this note, the attacks of three coexisting phorid species (Myrmosicarius grandicornis Borgmeier, Apocephalus attophilus Borgmeier and Neodorhniphora bragancai Brown) against Atta bisphaerica Forel workers in a pasture located in Viçosa County, Minas Gerais State, Brazil, are reported. The first two species of phorids are known to parasitize other leaf-cutting ants. N. bragancai, however, has been found only around A. bisphaerica nests. Each of these phorid species selects ants engaged in different tasks and oviposits in specific sites of the ant body. Moscas da família Phoridae parasitam várias espécies de formigas, inclusive diversas saúvas (Atta spp.). Nesta nota são relatados ataques de três espécies de forídeos (Myrmosicarius grandicornis Borgmeier, Apocephalus attophilusBorgmeier e Neodohrniphora bragancai Brown) contra operárias de Atta bisphaerica Forel em uma área de pastagem localizada em Viçosa, Minas Gerais. As duas primeiras espécies já são conhecidas como parasitóides de outras saúvas, mas N. bragancai foi recentemente descrita e encontrada somente ao redor de ninhos de A. bisphaerica. Cada uma dessas espécies de forídeos seleciona operárias que realizam diferentes tarefas e oviposita em partes específicas do corpo do hospedeiro.

Early season infestations of the sweet potato whitefly,Bemisia tabaci (Gennadius), on cantaloupes,Cucumis melo L., were determined by counts of the number of adults per leaf in fields near Yuma, Arizona. We used these data to develop binomial sampling plans based on the relationship between mean densities of whiteflies per leaf,m, and proportion of leaves infested with more thanI whiteflies,P I, according to the empirical model lnm=a′+b′ ln[−ln(1−P I)]. The models were developed for the presence-absence approach (I=0) and for a cutoff value of three whiteflies per leaf (I=3). Four independent data sets were used to evaluate the models. Both methods yielded reliable predictions at low infestation levels, but some of the higherm values were overestimated. As the tentative economic threshold forB. tabaci is three adults per leaf, which corresponds to lowP I values, results of the binomial sampling were satisfactory for pest management purposes.

1 We used a meta-analysis to evaluate the hypothesis that diversified crops are subject to lower density of herbivorous insects. This method consists of integrating findings of independent studies by calculating the magnitude of treatment effects (effect size). 2 A literature review covering a period of over 10 years yielded twenty-one studies that contained sufficient information for the meta-analysis. The data were analysed according to three criteria: yearly replications of the same study were considered independent data so that research repeated over time would have greater weight; a second meta-analysis was conducted with results of only 1 year because of possible lack of independence between results of the same study; the third approach was to remove studies involving Brassica spp. from the analysis because they are redundant from the standpoint of testing a general hypothesis of crop diversification. 3 The three analyses resulted in effect sizes of 0.50, 0.35 and 0.27, respectively, and all were statistically significant. These results correspond to 69%, 63% and 60% differences between average insect densities for treatment (diversified crops) and control groups. 4 We considered the last criterion for data analysis as the most appropriate because of lowest bias from non-independence between samples. Therefore we concluded that crop diversity caused moderate reduction of herbivorous insect populations. 5 The implications and limitations of meta-analyses are discussed.

Infestations of the sweetpotato whitefly, Bemisia tabaci (Gennadius), in fields of spring-grown cantaloupes, Cucumis melo L., near Yuma, AZ, were measured by counts of eggs, first to mid-fourth instars, late-fourth instars (red-eyed nymphs) and adults. All stages were sampled from leaves at the terminal and crown portions of the plant. Adults were sampled at 0700 and 1300 hours on the entire leaf, and immature stages were counted in a 1-cm2 area from each of four quadrants of a leaf. Adult whiteflies were more abundant on samples collected at 0700 hours and on terminal leaves in all fields. There were no significant differences between leaf sections for any immature life stage, but red-eyed nymphs were more abundant on crown leaves, whereas eggs had higher densities on terminal leaves. The power law and patchiness regressions indicated that all life stages were aggregated, but there were distinct degrees of aggregation between leaf positions.

The effects of agroecosystem diversification on the most abundant herbivore species of soybean ( Glycine max Merrill) in Ohio were monitored during 1988, 1989 and 1990. Maize and soybean plots were arranged in a randomized complete block design with four replicates for a 3 × 2 factorial experiment. Factors were cropping systems (maize monoculture, soybean monoculture and strip intercropping of maize and soybean) and tillage systems (no-tillage and conventional tillage). The herbivore fauna of soybean was sampled by sweep net and suction net (D-Vac). Statistically significant results from at least 1 year indicated that no-tillage was favorable to Japanese beetle ( Popillia japonica Newman), grape colaspis ( Colaspis brunnea (F.)), tarnished plant bug ( Lygus lineolaris (Palisot de Beauvois)), homopterans (Cicadellidae and Cercopidae), grasshoppers ( Melanoplus spp.) and slugs (Gastropoda). Potato leafhopper ( Empoasca fabae (Harris), green cloverworm ( Plathypena scabra (F.)), and striped flea beetles ( Phyllotreta spp.) were more abundant in conventional tillage plots. Strip intercropping was favorable to green cloverworm, Japanese beetle, and grape colaspis, whereas the potato leafhopper were more abundant in monoculture plots. There was no evidence of reduced herbivory in diversified agroecosystems, as predicted by the resource concentration hypothesis.

Corn (Zea mays L.) and soybean (Glycine max Merrill) were planted in monoculture and strip-intercropping plots (18.3 times 15.5 m each) under conventional tillage and no-tillage to create differences in habitat structure. The effects of these agronomic practices on carabid beetle species composition were measured by pitfall-trap collections during three years. Although neither the number of individuals or number of species were significantly affected by treatments, analyses of variance indicated that four of the six dominant species (75.7% of the total number of carabids captured in three years) responded to tillage treatments. Harpalus pensylvanicus DeGeer and Cyclotrachelus sodalis (LeConte) were more abundant in no-tillage plots, whereas Pterostichus chalcites Say and Scarites substriatus Haldeman were more common in conventional tillage plots. Pterostichus chalcites was also significantly more abundant in soybean plots than in intercropping or corn plots. H. pensylvanicus, a primarily herbivorous carabid, was the most common species collected. However, P. chalcites, a predaceous carabid, was the dominant species in soybean/conventional tillage plots. The results suggest that characteristics of individual species should be carefully considered for studies of communities such as carabid beetles, which have few strongly dominant species and a wide range of resource utilization.

Because the size of Atta spp. along foraging trails is partly determined by the characteristics of the plants harvested, and considering that parasitic phorid flies are attracted mostly to large individuals, we hypothesized that plant toughness affects the susceptibility of Atta spp. to these parasitoids. To test this hypothesis, we evaluated parasitism rates of the phorid Neodohrniphora sp. and its effect on Atta sexdens (L.) foragers in a laboratory colony. We manipulated forager size by alternating tough (Anthocephalus chinensis, Rubiaceae) and tender (Rosa chinensis, Rosaceae) plants given to the colony. Ants foraging on tough leaves were larger than ants foraging on soft leaves, and there was a significant reduction in forager size for both plants when the colony was exposed to Neodohrniphora sp. However, there were no relative differences on forager size between the two plants after the introduction of the parasitoid. The lack of response of Neodohrniphora sp. to the increase in ant size when the colony was given tough leaves may be attributed to the unusually large number of suitable hosts in a laboratory colony. However, large foragers are much less abundant in the field, in which case shifts in the size of the workforce triggered by different substrates could affect the incidence of parasitism.

We tested two agronomic practices that are likely to increase plant and structural diversity, no-tillage and strip intercropping, for effects on corn invertebrate fauna. Some of the most common herbivores and natural enemies were sampled by direct counts and damage estimation from 1988 through 1990 on monoculture corn and strips of corn alternated with soybean, under no-tillage and conventional tillage. Among soil pests, cutworms (mostly the black cutworm, Agrotis ipsilon (Hufnagel)); armyworm, Pseudaletia unipuncta (Haworth); and slugs (Gastropoda) were more abundant in no-tillage plots, although only slugs caused severe damage. The western corn rootworm, Diabrotica virgifera virgifera LeConte, and the European corn borer, Ostrinia nubilalis (Hubner), were generally more abundant in conventional tillage plots. Despite crop rotation, the strip-intercropping system (four rows of each crop) was less effective in reducing western corn rootworm infestation, especially in conventional tillage plots. In 1990 only, ladybugs (mostly Coleomegilla maculata (DeGeer)) were more abundant in conventional tillage plots, whereas tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois), were more abundant in notillage plots. Japanese beetle, Popillia japonica Newman; stink bugs, Acrosternum hilare (Say) and Euschistus servus (Say); and spiders (Aranea) were not significantly affected by treatments.

Male euglossine bees were sampled with chemical baits every two months from September 1997 to July 1999 at nine sites in the Desengano mountain range, Rio de Janeiro State, Brazil. Four sites were located in Atlantic Forest mature second growth, two sites in disturbed forest, and three sites in forest fragments of 200, 156, and 14 ha, respectively. We collected 3653 male euglossine bees from at least 21 species. Analyses of variance indicated no differences among the three habitat types for total number of bees, and 5 of the 6 dominant species. Bootstrapping indicated significant variation in species richness and diversity for some sites, but there was no clear indication of differences among habitats. Similarity as measured with the Morisita–Horn index was inversely related to distance between sites, but relatively high for most site combinations. These results suggest that the euglossine bee community in the three habitats was essentially the same. Although some species were associated with each habitat type, most appeared to respond to temporal local conditions. Our results do not support the hypothesis that forest fragmentation or habitat alteration reduces abundance and diversity of euglossine bees.