358 INSECTA. 



eggs on his lips. The larvae cling to his tougue, and descend through 

 the esophagus into the stomach, where they feed on the humour se- 

 creted by its lining membrane. They are usually found round the 

 pylorous, and rarely in the intestines. They are frequently suspended 

 there, in clusters, in great numbers. M. Clark however is of opinion, 

 that they are rather useful to the animal than injurious. 



The larvae of the CEstri are usually conical and destitute of feet. 

 Their body, exclusive of the mouth, is composed of eleven annuli, co- 

 vered with little tubercles and small spines, frequently arranged like 

 cords, that facilitate its progression. The principal organs of respir- 

 ation are situated on a squamous plane of the posterior extremity of 

 body, which is the largest. It appears that their number and disposi- 

 tion are different in the gastric larvae. It also seems that the mouth 

 of the cutaneous larvae is only composed of mammillae, whilst that of 

 the internal ones is always armed with two stout hooks. 



Both kinds, having acquired their growth, leave their abode and 

 fall to the ground, in which they concealed themselves, in order to 

 become pupae, under their own skin, like other Diptera of this family. 

 Those which inhabit the stomach follow the track of the intestines, 

 and aided perhaps by the foecal discharge of the animal, escape per 

 anum. These metamorphoses usually occur in June and July. 



M. de Humboldt met with Indians in South America, whose abdo- 

 men was covered with little tumours, produced, as he presumed, by 

 the larvae of an CEstrus. More recent observations seem to corrobo- 

 rate this opinion. They perhaps belong to some species of the genus 

 CuTEREBRA of M. Clark, whose larvae live under the skin of certain 

 Mammalia, 



It would also appear, that larvae, analogous to those of the CEstrus, 

 have been withdrawn from the maxillary or frontal sinuses of Man ; 

 but these observations have not been sufficiently prosecuted *. 



* In the second eidition of the Nouv. Diet. d'Hist. Nat., article (Estre, I have 

 published a new systematic arrangement of these Insects. 



Some have a very distinct and retractile proboscis : the genus Cuterebra of 

 M. Clarck, and the Cephenemyia, Lat. In the first, the seta of the antennae is 

 plumous, and the palpi are not apparent. The (Estrus huccatus of Fabricius belongs to 

 this genus. M. Clarck has described another species, the cuniculi, and I have pub- 

 lished a third, the ephippium; they are all from America. The seta of the antennae 

 is simple in the Cephenemyise, and the palpi are apparent. The CEstrus trompe, Fab., 

 is the type of the genus. 



The others are destitute of a proboscis : the seta of the antennae is always sim- 

 ple. Two palpi are Still visible in the (Edemagena, a genus established on the 

 (Est. tarandi. 



In the three following genera they disappear. 



The Hypodermae — Hypoderma — have a small oval slit in the form of a Y. Such 

 is the character of the CEstrus bovi. The Cephalemyiae — Cephalemyia — have two 

 very small, punctiform tubercles, which are vestiges of the palpi. The wings are 

 distant, and the alulae cover the halteres — CEstrus ovis. In the [CEstri— CEstrus — 

 these two tubercles also exist, but the wings are crossed on their inner margin, 

 and the alulae only cover a portion of the halteres — CEstrus equi, Fab., and some 

 others. M. Meigen calls this last genus Gastrus; it is the Gasterophilus of Dr. 

 Leach. All the others, according to these gentlemen, form the single genus (Estrus. 

 Here, the posterior cells are closed by transverse nervures, before they reach the 

 posterior margin; in Gastrus, they are closed by that margin. We have described 

 these and some other characters in the Nouv. Diet, d'llist. Nat., article CEsfre. 



