Morphological Caste Differences in Some Neotropical Swarm-founding Polistine Wasps : II. Polybia dimidiata (Hymenoptera, Vespidae)

A distinct dimorphism between queens (inseminated egg-layers) and workers (uninseminated non-egg-layers) was found in a colony of Polybia dimidiata collected in Ribeirao Preto, southeastern Brazil. Mean sizes (or number) of 20 out of 24 body parts of the queens (n=30) were statistically smaller than those of workers (n=270), while queens were larger only in two parts, i.e., mesosomal height and apical width of tergite II (t-test, p<0.05). The Q/W ratio in the alitrunk length was 0.87, indicating the queen dwarfism in this species. The canonical discriminant analysis also showed clear dimorphism with a Mahalanobis's intercaste distance (D^2) 6.76. Some caste-linked color differences occurred on head, mesosoma and metasoma where the discriminant morphological characters were detected. Besides, castes also differed in pronotal contour and RICHARDS' gland.