Reproductive castes are compared in species of swarming wasps representing all currently recognized genera of Epiponini (Polistinae). New morphometric data for nine measures of body parts and ovarian data are presented for 13 species. These are integrated with all similarly conducted available studies, giving a total of 30 species. Analysis reveals several syndromes relating reproductive and nonreproductive individuals: no meaningful distinction, physiological differences only, reproductives larger than nonreproductives with intermediate individuals present, reproductives different in shape from nonreproductives with no intermediates, and reproductives smaller in some aspects than nonreproductives. Distribution of these syndromes among species is consistent with phylogenetic relationships derived from other data. Optimizing these syndromes on the cladogram indicates that the basal condition of Epiponini is a casteless society that is not comparable to the primitively social genus Polistes where dominant queens control reproduction. Castes originate several times in Epiponini, with different results in different lineages. The best documented evolutionary sequence passes from casteless societies, to those with reproductives larger, to those with reproductives differing in shape from nonreproductives, to those with reproductives smaller in some measures. This sequence is consistent with Wheeler's theory of the origin of caste through developmental switches, and represents the most thorough test of that theory to date.

SUMMARYBees generate thoracic vibrations with their indirect flight muscles in various behavioural contexts. The main frequency component of non-flight vibrations, during which the wings are usually folded over the abdomen, is higher than that of thoracic vibrations that drive the wing movements for flight. So far, this has been concluded from an increase in natural frequency of the oscillating system in association with the wing adduction. In the present study, we measured the thoracic oscillations in stingless bees during stationary flight and during two types of non-flight behaviour, annoyance buzzing and forager communication, using laser vibrometry. As expected, the flight vibrations met all tested assumptions for resonant oscillations: slow build-up and decay of amplitude; increased frequency following reduction of the inertial load; and decreased frequency following an increase of the mass of the oscillating system. Resonances, however, do not play a significant role in the generation of non-flight vibrations. The strong decrease in main frequency at the end of the pulses indicates that these were driven at a frequency higher than the natural frequency of the system. Despite significant differences regarding the main frequency components and their oscillation amplitudes, the mechanism of generation is apparently similar in annoyance buzzing and forager vibrations. Both types of nonflight vibration induced oscillations of the wings and the legs in a similar way. Since these body parts transform thoracic oscillations into airborne sounds and substrate vibrations, annoyance buzzing can also be used to study mechanisms of signal generation and transmission potentially relevant in forager communication under controlled conditions.

The pheromones used by several species of stingless bees for scent trail communication are generally assumed to be produced by the mandibular glands. Here we present strong evidence that in Trigona recursa these pheromones originate from the labial glands, which are well developed in the heads of foragers. Analysis of the behavior involved in scent marking shows that a bee extends her proboscis and rubs it over the substrate. A single scent marking event lasts for 0.59+/-0.21 s while the bee runs a stretch of 1.04+/-0.37 cm on a leaf. According to choice experiments the bees are attracted by a feeder baited with labial gland extract (84.2+/-6% of the bees choose this feeder) but repelled from a feeder baited with mandibular gland extract (only 27.5+/-13.1% of the bees choose this feeder). They do not discriminate between two clean feeders (49.6+/-3% of the bees at a feeder). 87+/-5.1% of bees already feeding leave the feeder after the application of mandibular gland extract whereas only 6.2+/-4.9% and 2.6+/-4% do so when labial gland extract or pure solvent was applied.

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-Scaptotrigona depilis uses a scent trail to guide newly recruited bees to a food source. (i) Behavioral experiments show an additional chemical marking at the food source. The bees had to choose between an unused feeder and a feeder, at which their nestmates had fed. 71 to 86% of the bees chose the used feeder where the foragers had left attractants. The used feeder also attracted bees when it was moved away from its original site to a new site halfway along the scent path or 20 m beyond it. (ii) The localization of a food source by S. depilis is very precise with regard to both direction and distance. When control feeders were 1.7 m, 8.5 m, and 17 m away from the experimental feeder (at 50 m from the nest) 97.5-100% of the recruits chose the experimental feeder where the foragers were feeding. When positioned beyond the used feeder the control feeder remained unvisited. We conclude, that markings left at the used feeder represent particular end point tags and differ from scent path markings. stingless bee / Scaptotrigona / scent marking / recruitment

-The two stingless bee species Melipona scutellaris and M. quadrifasciata recruit nestmates to a rich foraging site. We tested this with feeders up to 140 m away from the hive. Foragers of M. scutellaris communicated direction (up to 140 m) more accurately than distance (up to 30 m) whereas those of M. quadrifasciata communicated direction only up to 30 m and distance up to 40 m. Our data indicate that in both species recruitment is divided into two temporal phases. Whereas in an initial phase alarmed nestmates search for food at random, bees leaving the hive in the following phase are obviously provided with information about its specific location. As a consequence after 35 minutes (M. scutellaris) and 85 minutes (M. quadrifasciata), respectively, significantly more newcomers arrive at the feeder than at an identical control feeder. The differences found in the recruitment success of M. scutellaris and M. quadrifasciata are discussed in regard to the different demands of their natural habitats.

In neotropical swarm-founding wasps, caste differences can be arranged along a spectrum ranging from taxa in which queens and workers are externally similar, to others with fairly distinct caste attributes. In this study, queen-worker differences progressively increase during colony development in Protopolybia exigua and Chartergus globiventris. In Apoica flavissima, morphological caste differences are clearly pre-imaginally determined and have no variation in different phases of the colony cycle. Non-inseminated layers are abundant in P. exigua during the whole colony cycle, restricted to some phases in C. globiventris, and completely absent in A. flavissima. Based on these reported traits plus data from the literature, social regulation in epiponine castes can be morphologically and reproductively fixed, morphologically fixed but reproductively inducible depending the colony cycle, reproductively inducible throughout colony cycle, or reproductively inducible throughout colony cycle only in some periods.Research article 63 individuals were measured and dissected. In large colonies where castes were hard to identify, one hundred individuals were chosen randomly. After identifying some morphological characters to discriminate queens, such as abdominal size, all individuals having such a pattern were collected and used in the analysis. The following characters were measured under a binocular microscope with an ocular micrometer (smallest unit = 0.01 mm): head width (HW), minimum interorbital distance (IDm), width of mesoscutum (MSW), alitrunk length (AL), basal width of tergite II (T 2 BW), and partial length of the forewing (WL). Ovary condition was determined by dissection under a stereomicroscope. The spermatheca from each dissected female was removed and put on a slide in a 1 :1 solution of glycerin and alcohol (70 %) in order to check for insemination under a microscope. Before statistical analysis, data were log transformated in order to avoid problems of variance. Two groups, queens with ovarian development and insemination and workers regarding the remaining females, were determined for statistical purposes. Means and standard deviations were calculated from the five morphological measurements. Oneway ANOVA was used for mean comparisons. The contribution of each variable to caste discrimination was examined using discriminant function analysis using the stepwise method (Rao, 1973). In this method, variables are successively added to the model based on the higher F to enter values, adding no more variables when the F-ratio is no longer significant. Stepwise addition of variables sometimes results in models where variables may be included although they no longer explain a significant fraction of the variance. Wilks' Lambda values were used to infer the individual contribution of each variable to the model. The Wilks' lambda statistic for the overall discrimination is computed as the ratio of [the determinant of the within-groups variance/covariance matrix] to [the determinant of the total variance/covariance ...

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