358 INSECTA. 
eggs on his lips. The larve 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 larve of the Céstri 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 larvee. It also seems that the mouth 
of the cutaneous larve is only composed of mammille, whilst that of 
the internal cnes is always armed with two stout hooks. 
Both kinds, having acquired their growth, leave their abode and 
fall tothe ground, in which they concealed themselves, in order to 
become pupz, 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 larvee of an CEstrus. More recent observations seem to corrobo- 
rate this opinion. ‘They perhaps belong to some species of the genus 
Cureresra of M. Clark, whose larve live under the skin of certain 
Mammalia. 
It would also appear, that larvee, analogous to those of the (Estrus, 
have been withdrawn from the maxillary or frontal sinuses of Man; 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. Dict. d’Hist. Nat., article @stre, 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 antennz is 
plumous, and the palpi are not apparent. The strus buccatus 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 antenne 
is simple in the Cephenemyiz, and the palpi are apparent. The Gistrus trompe, Fab., 
is the type of the genus. 
The others are destitute of a proboscis: the seta of the antenne is always sim- 
ple. Two palpi are still visible in the @pEMAGENA, a genus established on the 
Gst. tarandi. 
In the three following genera they disappear. 
The Hypoderme—H yPoDERMA—have a small oval slit in the form of a Y. Such 
is the character of the Cstrus bovi. The Cephalemyie—CEPHALEMYIA—have two 
very small, punctiform tubercles, which are vestiges of the palpi. The wings are 
distant, and the alule cover the halteres—Cstrus ovis. In the {Cstri—Gistrus— 
these two tubercles also exist, but the wings are crossed on their inner margin, 
and the alule only cover a portion of the halteres—Mstrus 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 Cstrus. 
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. Dict. d’Hist. Nat., article Gstre. 
