A Possible Explanation for Size Differences in the Metapleural Glands of Ants (Hymenoptera: Formicidae)

Posterior thoraces of the queen, male and worker castes of the bull ants Myrmecia gulosa F. and M. urens Lowne were examined by light and scanning electron microscopy. Metapleural glands are present in queens and workers but absent in males. There are differences in gland size and cell number, both between species and between queen and worker castes. Our data, together with previously published data, show that cell number is positively correlated with overall body size, suggesting that variation in gland size is functionally related to surface area. Because metapleural secretions have strong antibiotic properties, this relationship may be to provide sufficient secretion to cover the integument.