Multiporous plate sensilla in antennae of the chalcidoidea (Hymenoptera)

Abstract

The ultrastructure of one sensillar type in one group of insects is described so that comparisons of this structure with similar structures in different groups of insects might be made. The ultrastructure of multiporous plate sensilla (MPS) in antennae was studied in 13 species from 7 families of Chalcidoidea. The cuticle of the MPS consists of an elongated, porous plate elevated above the antennal surface. Two cuticular invaginations form 3 channels, a median channel and 2 lateral channels that extend through the length of the sensillum. The MPS are innervated by numerous neurons, more than 50 in some species. The dendrites extend towards the median channel at the proximal end of the sensillum. When the dendrites reach the median channel, they branch and turn towards the distal end of the sensillum, traversing its longitudinal axis. Pore tubules, which occur in the pore chambers, come in contact with the membranes of the dendritic branches. There are 2 types of MPS: (1) with a relatively thin porous plate and many pores occurring in females and males; (2) with a thicker porous plate and fewer pores occurring in females only. The MPS in the Chalcidoidea are compared with the MPS in other Hymenoptera and the functional significance of the 2 types of MPS in the Chalcidoidea is discussed.