The maxillary palp sensory pathway of Orthoptera.

Primary sensory projections and arborisations of higher-order neurons associated with the maxillary palps were examined in Tettigoniidae, Gryllidae, Tetrigidae and Acrididae representing the two sub-orders of Orthoptera, Ensifera and Caelifera. Anterograde filling and Golgi impregnation of maxillary receptor neurons revealed two patterns of innervation, the ensiferous and the caeliferous type. In both ensiferans and caeliferans, receptor neurons arborised within the tritocerebrum, the antennal motor- and mechano-sensory centre and the lobus glomerulatus. In ensiferans, additional areas of innervation were found in the lobus glomerulatus and in a previously undescribed neuropil, here referred to as the accessory lobus glomerulatus. In relation to the anatomical data a putative functional segregation of the neuropil into gustatory-, olfactory- and mechano-sensory centres is implied.