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 larvcE : it also appears that the mouth of the cutaneous 

 larvae is only composed of fleshy lobes, whilst that of the internal larvse is armed with two strong, 

 bent hooks. 



^Yhen the larvae have oljtained 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 (Estri 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 antennse plumose, and the palpi not visible. OSstrus buccaius, Fab. ; 

 CunieuU, Clark ; and Epkippium, Latr. ; all from America. 



Cephenemyia, Latr., has the seta simple, and the palpi evident. CEstnis Trompe, Fab., the larva of which infests 

 the frontal sinus of the Rein-deer. 



The others have no proboscis, and the seta of the antennas is always simple. 



(Edemagena, Latr., has two palpi. CEstrus Tarandi, the Bot of the Rein-deer. 



The following- have no palpi. 



Ui/poderma, Latr., with a small oral aperture like a Y. CEstrus Bovis, the larva of which resides in tumours on 

 the back of Oxen. 



Ceplialemijia, Latr., has two small tuberclee like points, which are the vestiges of palpi ; the alulets cover the 

 balancers. CEstrus Ovis, the Sheep Bot-lly, the larva of which lives in the frontal sinuses of the Sheep. 



CEstrus proper {Gasfrus, Meig., Gasierophilus, Leach), has two similar tubercles, 

 but the wings cross each other, and the alulets only partially cover the halteres. 



CEstrus Equi, the Great Horse Bot, hamorrhoidalis, vetmnus, &c. This differs 

 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 CEstrus) the cells are closed before reach- 

 ing the hind margin. 



The third tribe of the Athericera, that of the Conopsari.e, 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. IM.— Gasterophilus equi CONOPS, LinUaeUS. 



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. (Cepkenes, Latr.), has the antenna; 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 riifipes, Fab., which undergoes its transformations in the interior of the body of living Bombi, escaping 

 between the segments. An apod larva, found in Bombus lapidarins, being probably that of this species, has fur- 

 nished IMessrs. Amlouin and Lachat materials for some fine anatomical observations. 



Zodion, Latr., has the antennse shorter than the head, terminating in an ovoid mass. 



Mi/opa, Fab., has the proboscis elbowed at the base, and again near the middle, the apex being bent under, and 

 the antennae shorter than the head. [Several British species.] 



The others {Stornoxydm, ileig.), resemble domestic FHes in their general form, the arrangement of 

 their wings, the antennas 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. Tj-pe, Conops calcitrans, Linn, [a very common 

 insect, often observed on windows, and which is the species] which pricks our legs so sharply, especially 

 before rain. 



