The Post-embryonic Development of Phaenoserphus viator Hal. (Proctotrypoidea), a Parasite of the Larva of Pterostichus niger (Carabidae), with Notes on the Anatomy of the Larva

Abstract

1. The life-history of Phaenoserphus viator is described.Four larval instars are found, endoparasitic in the larvae of Pterostichus niger. At thee nd of the last larval instar the parasites, which may number as many as 45 in a single host, emerge, and while still attached, pupate without spinning a cocoon.Adults may appear in August or September.The effect of the parasite in inhibiting metamorphosis of the host is discussed.2. The first observed larva is atracheate and incompletely segmented at first and is of the polypod type bearing paired prolegs on the body segments.Subsequent instars are apodate.The tracheal system develops progressively in the several instars, but only becomes functional in the final stage.3. The anatomy of the larva is briefly described with the exception of the musculature.Tracheal development is described. Gas only appears in the tracheae after the development of the tracheole cells puts the tracheae into communication with the body wall and other organs.In the circulatory system an important accessory organ is the neural sinus, formed by the enclosure of the ventral nerve cord beneath a connective tissue curtain.The imaginal discs of the hypodermis are briefly described, these being clearly defined in the head, thorax, and posterior abdominal segments.The nervous system consists of a brain, suboesophageal ganglion and 11 ventral ganglia, the most posterior being tripartite. This system is connected with the sympathetic, by nerves passing from the cerebral commissures to a frontal ganglion which lies above the oesophagus and behind the labrum.