A Proprioceptor in the Body Musculature of Lepidoptera

Abstract

DURING a study of muscle histolysis in saturniid moths¹, sense organs were found in association with the intersegmental muscles. So far as we can ascertain, they are of a type not previously described for insects. They resemble the receptors discovered by Alexandrowicz² in the Crustacea. Each receptor consists of a modified muscle fibre in which the striations are faint, but which is capable of contraction. In the final instar larva of Antheraea pernyi, there is a pair of these receptors in the meso- and meta-thorax and in abdominal segments 1–9. The receptors lie in the dorsal longitudinal muscles¹ and are attached to the epidermis at the intersegmental folds. They persist during metamorphosis and are present in the abdomen of the pupa and adult, but so far they have not been located in the thorax of these stages. Near the middle of the fibre, a swelling is formed by an ovoid sac filled with an unidentified substance which stains with some nuclear stains such as hæmatoxylin and celestin blue. Attached to the receptor at this point is a single large sensory neurone the dendrites of which enter a fibre tract running the full length of the receptor. The fibre tract appears to be composed of connective tissue fibres. A rich motor innervation is present, with nerve endings at intervals all along the organ. Similar receptors have been found in Platysamia cecropia, Telea polyphemus, Samia walkeri and Actias selene.