CENTRAL PROJECTIONS OF THE SENSORY HAIRS ON THE GEMMA OF THE ANT DIACAMMA - SUBSTRATE FOR BEHAVIORAL MODULATION

In the ant genus Diacamma, all workers eclose from their cocoons with little clublike thoracic appendages, called gemmae. Whether these gemm ae are mutilated determines individual behaviour, and ultimately repro ductive role, in two of the three species examined. The gemmae are cov ered with sensory hairs, which probably serve a mechanoreceptive funct ion. The sensory afferents arising from these hairs were stained and t raced into the central nervous system (CNS). They feature widely distr ibuted collaterals invading all three thoracic ganglia as well as the suboesophageal and the second abdominal ganglia. The multisegmental ar borization pattern of the gemma afferents is very similar to that of w ing-hair afferents of other ants (queens and males) or other insects i n general. This implies that gemmae and wings are homologous structure s. We discuss the morphology of the gemma afferents with respect to th eir possible involvement in the behavioural changes associated with mu tilation. The neuronal processing may be modulated by (1) the decrease of sensory input onto interneurons (suggested by the afferents' exten sive arborizations); or (2) by the effect of neuromodulatory substance s (suggested by the finding that terminals occur within the cell body rind of the ganglion).