Dipterous Genus Conops. 287 



thistle. This Ponip'/lus, whose visits on such occasions would 

 appear to be directed rather to the object of obtaining nutriment 

 for itself, tlian to tliat of supplying ravin for its larva brood, — 

 judging from its disinclination to rise after alighting, so unlike the 

 quivering restlessness of the PompUi in general,- — has already at 

 this period, when under the influence of parasitic gestation, the 

 Conops larva feeding within its abdomen, and diverting to itself all 

 the sustenance provided by the former. 



These Pompili soon perish after capture, rarely surviving 

 beyond the second day. On separating the posterior portion of 

 the abdominal region below the fourth segment, the parasite is 

 readily perceptible, and its condition of development recognizable ; 

 nor does this operation upon the defunct Pompilus in any way 

 interfere with the subsequent metamorphosis of the parasite, 

 should the indispensable requirements of its larva growth be 

 already fulfilled at the time. 



The head of these larvae, very much contracted in proportion to 

 the rest of the parasite, is capable of being extended into juxta- 

 position with the base of the abdomen of its victim, by mtans of 

 two or three telescopic tubular processes, which, on gently pressing 

 the anterior part of the body, are projected forwards. 'J'he outer 

 tegument of these is very slender and diaphanous ; the apex has 

 the appearance of a smooth rounded nipple, slightly impressed in 

 the middle; at a considerable distance below wliich, and almost 

 concealed within the flesliy substance of the interior, are perceived 

 two dusky points, which, when denuded of the surrounding 

 matter, are found to indicate the position of two corneous hooks, 

 slightly curved, the tips acute and turned outwardly, the base 

 dilated at the inner angle and produced into a point shorter than 

 the main body of the hook. In one specimen these hooks were 

 visible on first inspecting the larva, resting precisely in the centre 

 of the anterior part of the head ; but, on applying pressure, 

 instead of being projected forwards retaining their anterior 

 position, the telescopic tubes were protruded beyond and over 

 them, the hooks remaining in the rear. 



The anal extremity of the Conops larva, which at its period of 

 greatest development is closely assimilated in dimensions to the 

 largest diameter of the abdominal cavity, is furnished with two 

 remarkable appendages, or reniform densely rugose lobes, de- 

 flexed side by side from the dorsal region posteriorly, concave 

 within, and connected througliout their crenulated margin with 

 the anal segment, the more distended portion towards the ventral 



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