The structure of the cercal sensory system and ventral nerve cord of Grylloblatta. A comparative study.

The structure of cercal sensilla, the cercal nerve and the central projections of the cercal sensory nerve of a notopteran (Grylloblatta sp.) are described and compared with other orthopteroid insects in which the cercal sensory system and central connections are well known. The cercal sensilla are similar to those of gryllids and blattids, but the gross structure of the cerci and distribution of cercal sensilla more closely resemble those of the Thysanura. The elements of the cercal sensory nerves and the central nervous system are similar to those of other orthopteroid insects, but extracellular material is present in greater quantity, and more extensive glial bundling of axons occurs in both the cercal nerve and central connectives. Glial structure, extracellular material and large multicristate mitochondria may be adaptations to life near O degrees C. The form of central projections of the cercal nerve and the configuration of the largest abdominal interneurons are unlike those of gryllids and Dictyoptera; they are similar to those of Dermaptera.