DIPTERA. 631 
scaly plate at the posterior extremity of the body, which is thickest. It appears that their number 
and arrangement are different in the gastric larvae : it also appears that the mouth of the cutaneous 
larvae is only composed of fleshy lobes, whilst that of the internal larvae is armed with two strong, 
bent hooks. 
When the larvae have obtained their full size, they quit their former abode, fall to the earth, and 
there hide themselves, in order to undergo those transformations to pupae beneath their own skin, like 
the other Diptera of this division. The gastric larvae pass through the intestines and escape by the 
anus, probably with the excrement. It is generally in June and July that these changes take place. 
M. Humboldt has observed, in South America, Indians with the abdomen covered with small 
tumours, produced, as he believed, by the larvae of (Estri ; and later observations appear to confirm 
this opinion. These larvae probably belonged to the genus Cuterebra of Clark, the larvae of which 
reside beneath the skin of several mammiferous animals. It also appears, from various testimony, 
that larvae analogous to those Qilstri have been extracted from the maxillary or frontal sinuses of 
Man ; but these observations have not been pursued. 
Some have a small and retractile proboscis. 
Cuterebra, Clark, has the seta of the antennae plumose, and the palpi not visible. (Estrus buccatus, Fab. ; 
Cuniculi, Clark ; and Ephippium, Latr. ; all from America. 
Cephenemyia, Latr., has the seta simple, and the palpi evident. (Estrus Trompe, Fab., the larva of which infests 
the frontal sinus of the Rein-deer. 
The others have no proboscis, and the seta of the antennae is always simple. 
(Edemagena, Latr., has two palpi. (Estrus Tarandi, the Bot of the Rein-deer. 
The following have no palpi. 
Hypoderma, Latr., with a small oral aperture like a Y. (Estrus Boris, the larva of which resides in tumours on 
the back of Oxen. 
Cephalemyia, Latr., has two small tubercles like points, which are the vestiges of palpi ; the alulets cover the 
balancers. (Estrus Ovis, the Sheep Bot-fly, the larva of which lives in the frontal sinuses of the Sheep. 
(Estrus proper (Gastrus, Meig., G aster op Jiitus, Leach), has two simitar tubercles, 
but the wings cross each other, and the alulets only partially cover the halteres. 
(Estrus Equi, the Great Horse Bot, hcemorrhoidalis, vederinus, &c. This difiers 
in the cells, extending to the hind edge of the wings, whereas in all the rest (which 
Leach and Meigen retain under the name of (Estrus) the cells are closed before reach- 
ing the hind margin. 
The third tribe of the Athericera, that of the CoNOPSAuiiE, is the only 
one in which the proboscis is always exserted and siphon-shaped, either cylin- 
dric, conical, or setaceous. The reticulation of the wings is the same as in 
our first division of Muscides. The majority of these insects are found on 
plants. They compose the genus 
Fig. 136.— Gasterophilus equi. CONOPS, LinuagUS. 
Some have the body long and narrow ; the abdomen long, clavate, and bent under at the tip, with 
the male organs exposed. 
One portion of these has the proboscis only elbowed at the base. 
Systropus, Wied. {Cephenes, Latr.), has the antennae much longer than the head, the last joint alone forming 
the club, without a style, and the abdomen long and slender. South American insects, like small species 
of Sphex. 
Conops proper, has the antennae much longer than the head, and the last two joints form together a mass, with 
a terminal style. 
Conops rufipes, Fab., which undergoes its transformations in the interior of the body of living Bombi, escaping 
between the segments. An apod larva, found in Bombus lapidarius, being probably that of this species, has fur- 
nished Messrs. Audouin and Lachat materials for some fine anatomical observations. 
Zodion, Latr., has the antennae shorter than the head, terminating in an ovoid mass. 
Myopa, Fab., has the proboscis elbowed at the base, and a^ain near the middle, the apex being bent under, and 
the antennae shorter than the head. [Several British species.] 
The others {Stornoxydos, Meig.), resemble domestic Flies in their general form, the arrangement of 
their wings, the antennae terminated by a palette shorter than the head, and furnished with a seta, 
and the abdomen short and conical, without external appendages. 
Stomoxys proper, has the proboscis only elbowed at the base. Type, Conops calcitrans, Linn, [a vei*y common 
insect, often observed on windows, and which is the species] which pricks our legs so sharply, especially 
before rain. 
