The Dufour's gland and the cuticle in the social wasp Ropalidia marginata contain the same hydrocarbons in similar proportions.

Queens in many social insects are known to maintain their status through chemicals (pheromones) and cuticular hydrocarbons and have been the focus of many investigations that have looked at the chemicals involved in queen signaling. In the primitively eusocial wasp Ropalidia marginata Lepeletier (Hymenoptera: Vespidae), the Dufour's gland has been shown to be involved in queen signaling, and Dufour's gland hydrocarbons have been found to be correlated with fertility. Hence, this study analyzed the cuticle of R. marginata along with the Dufour's gland in order to compare their hydrocarbon profiles. The results show that the Dufour's gland and cuticle contained the same set of hydrocarbons in similar proportions (for the majority of compounds). Patterns pertaining to fertility signaling present in cuticular hydrocarbons were also similar to those present in the Dufour's gland hydrocarbons. Furthermore, the haemolymph contained the same hydrocarbons as found in the Dufour's gland and cuticle in similar proportions, thereby providing an explanation as to why the hydrocarbon profiles of the Dufour's gland and cuticle are correlated.

Polymorphic microsatellite loci for primitively eusocial wasp Ropalidia marginata.

We report here development and characterization of 48 novel microsatellite markers for Ropalidia marginata, a tropical, primitively eusocial polistine wasp from peninsular India. Thirty-two microsatellites showed polymorphism in a wild population of R. marginata (N = 38) collected from Bangalore, India. These markers will facilitate answering some interesting questions in ecology and evolutionary biology of this wasp, such as population structure, serial polygyny, intra-colony genetic relatedness and the pattern of queen succession.

TrialDB: A web-based Clinical Study Data Management System.

Clinical Study Data Management Systems (CSDMSs) are a class of software that support centralized management of data generated during the conduct of clinical studies. Commercial CSDMSs include Oracle Clinical, ClinTrial and MetaTrial. Such systems, which are typically deployed at an institutional or organizational level, must accommodate diverse types of data from different clinical domains that is generated by different groups of clinical investigators. Large-scale CSDMSs typically employ a high-end database engine that is usually accessed over an intranet or the Internet using Web-based technologies. CSDMSs in institution-wide use for a variety of clinical domains are best served by entity-attribute-value (EAV) modeling for the clinical data: all the commercial CSDMSs that we are aware of use EAV design. However, de novo development of EAV databases for data management is a challenging task. A large body of generic metadata-driven code must be developed before a basic EAV application can be written. Clearly, the availability of pre-existing software with the requisite functionality would be very valuable. We will discuss the benefits of such software being in open-source form.

Flexible division of labor mediated by social interactions in an insect colony-a simulation model

The primitively eusocial wasp Ropalidia marginata shows an age-based division of labor in which workers allocate tasks according to their relative ages (age ranks). This age polyethism seems quite flexible because in colonies devoid of old workers, young individuals can perform the tasks normally performed by older workers. Social interactions appear to be a plausible mechanism by which workers can assess their relative ages. To explore possible proximate mechanisms that can potentially generate such a flexible, age-based task allocation, the activator-inhibitor model was adapted to the social biology of R. marginata and tested using computer simulations. The model generated a clear age polyethism including the phenomena of precocious foragers in colonies with only young individuals and reverted nurses in colonies consisting of only old individuals. A simple extension of the model to allow the brood:adult ratio to modulate the rates of social interactions, shows how increasing task demands can be met by a decrease in the ages of first performance of, and an increase in the proportions of individuals engaged in, various tasks. These results show how a pattern of division of labor based on relative age can be generated and modulated by social interactions. Copyright 1999 Academic Press.

Uniform discrimination of pattern orientation by honeybees.

To explore how honeybees, Apis cerana, discriminate the orientation of patterns, we trained workers to discriminate between a black stripe of a certain orientation on a white disc and a pure white disc. We tested trained bees for their ability to discriminate between the trained orientation and deviations from it. This was done either in a dual choice situation where the bees had to choose between the trained orientation and one deviation from it at a time, or in a multiple choice situation where bees had to choose simultaneously between the trained orientation and 11 successive deviations from it. In the dual choice situation, bees did not discriminate behaviourally between the trained orientation and deviations up to 25 degrees, whereas in a multiple choice situation, they discriminated between the trained orientation and a deviation of 15 degrees or more. Thus, orientation can be analysed more precisely in multiple choice experiments. The response of the bees was independent of the orientation of the trained orientation; the 12 different trained orientations all yielded identical results. This finding, considered together with a model that we present for orientation discrimination, suggests that at least three orientation-sensitive channels (a neuron or a set of neurons that respond maximally to a particular orientation) participate in the analysis of pattern orientation. (c) 1998 The Association for the Study of Animal Behaviour.

Erratum.

Gadagkar, R. Trends Ecol. Evol. 13, 122-123 (March 1998).

Demographic predisposition to the evolution of eusociality: a hierarchy of models.

I present a hierarchy of models that illustrate, within the framework of inclusive fitness theory, how demographic factors can predispose a species to the evolution of eusociality. Delayed reproductive maturation lowers the inclusive fitness of a solitary foundress relative to that of a worker. Variation in age at reproductive maturity makes the worker strategy more profitable to some individuals than to others and thus predicts the coexistence of single-foundress and multiple-foundress nesting associations. Delayed reproductive maturation and variation in age at reproductive maturity also select for mixed reproductive strategies so that some individuals whose reproductive maturation is expected to be delayed can first act as workers and later switch over to the role of a queen or foundress. Assured fitness returns shows how identical mortality rates can have different consequences for workers and solitary nest foundresses because a solitary foundress will have to necessarily survive for the entire duration of development of her brood, whereas a worker can hope to get proportional fitness returns for short periods of work. In concert with assured fitness returns, delayed reproductive maturation and variation in age at reproductive maturity become more powerful in selecting for worker behavior, and mixed reproductive strategies become available to a wider range of individuals. These phenomena provide a consistently more powerful selective advantage for the worker strategy than do genetic asymmetries created by haplodiploidy.

An undersirable property of Hill's diversity indexN 2.

A desirable property of a diversity index is that it be a convex function of the proportions of different species that constitute a community.N 2, a diversity index belonging to the Hill's series of diversity indices and which is equivalent to the reciprocal of Simpson's diversity index violates this requirement when the proportion of one of the species is close to 1. Recommendations ofN 2 as the best possible index of diversity therefore need to be examined judiciously.