DIPTERA. 287 
fall to the ground, in which they conceal themselves, in order to 
become pup 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 fcecal 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 larvz of an Gistrus. More recent observations seem to corrobo- 
rate this cpinion. They perhaps belong to some species of the 
genus Curerresra of M. Clark, whose larve live under the skin of 
certain Mammalia. 
It would also appear, that larve, analogous to those of an Cistrus, 
have been withdrawn from the maxillary or frontal sinuses of Man; 
but these observations have not been sufficiently prosecuted(1). 
CE. bovis, De Geer; Clarck., Lin. Trans., III, xiii, 1,6. From 
six to seven lines in length, and densely pilose; thorax yellow, 
with a black band; abdomen white at base, with a fulvous extre- 
mity; wings somewhat obscure. 
The female deposits her eggs under the hide of healthy Oxen 
and Cows, of not more than two or three years of age. The 
(1) In the second edition 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 Currresra of 
- M. Clarck, and the Crrnenremyia, Lat. In the first, the seta of the antenne is 
plumous, and the palpi are not apparent. The @strus buccatus of Fabricius be- 
longs to this genus. M. Clarck has described another species, the cuniculi, and 
I have published a third, the ephippium; they are all from America. The seta of 
the antennz is simple in the Cephenemyiz, and the palpi are apparent. The 
Cstrus trompe, Fab., is the type of the genus. 
The others are destitute of a proboscis: the seta of the antennz is always sim- 
ple. Two palpi are still visible in the (2nprmacena, a genus established on the 
st. tarandi. 
In the three following genera they disappear. 
The Hypoderme—Hyroperma—have a small oval slitin the form ofa Y. Such 
is the character of the @strus bovi. The Cephalemyie—Czrruatemy1a—haye 
two very small, punctiform tubercles, which are vestiges of the palpi. The wings 
are distant, and the alulz cover the halteres—(strus ovis. In the Géstri—(CEstrus 
—these two tubercles also exist, but the wings are crossed on their inner margin, 
and the alule only cover a portion of the halteres—(@strus 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 @strus. 
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 charactersin the Nouy. Dict. d’Hist. Nat., article @stre. 
