ANATOMY OK THE GOUT-FLY OP BARTiEY. 



785 



region of the third thoracic segment. At the latter region tlie 

 diameter tapers oft" rather rapid!}'' .'Ulteriorly to the minute head 

 and ver}"^ slightly and gradually posteriorly to the rounded anal 

 segment. The larva is apodous and of the usual Muscid type ; 

 I consider that it consists of a head, three thoracic and nine 



. . Text- figure 1. 



p.sp. 



G. tfEiiiojJus. Liitenil view of iiiatuve larva. 



abdominal segments. The larva is amphipneustic, the posterior 

 spiracles being at the apices of two very small papillie carried 

 postero-dorsally by the last abdominal segment. The anterior 

 spiracles lie one on each side, projecting from the first body-segment 

 near its posterior border, slightly dorsal to the mid-lateral line. 



The Head (text-fig. 2). . 



In 1904 Henneguy proposed the term " pseudo-cephalon " for 

 the anterior segment of Muscid larvte, and Hewitt (1914) follows 

 him in this nomencla.ture. Becker (1910), however, has shown 

 that the head of a Muscid larva is homologous with the head of 

 such a eucephalous type as the larva of Simulkcm, and there is 

 therefore no valid objection to the use of the term " iiead " iu 

 describing Muscid larvfe. 



The head is a small rounded body capable of almost complete 

 retraction within the fiivst borly-segment. Ventrall}^ it bears 

 several paired sense organs and also the mouth-opening tlirough 

 which project the a.pices of the mouth hooks; its surface is quite 

 smooth, with none of the chitinous ridges so commonly found on 

 the ventral surface of the head of cyclorrhaphous larvaD.' 



The most prominent cephalic sense oi'gans are tho maxillary 

 palps (m.p.), each of which consists of a small rounded group of 

 sense papillas suriounded by a dark brown chitinous ring. Each 

 sense papilla appears in surface view as a small shining ring with 

 a dark central region which is apparently a shallow depression at 

 the apex of the papilla. The two maxillary palps lie close to the 

 anterior border of the mOuth with their median borders almost 

 touching. From between- the tw^o maxillary palps a median 

 depression runs forwards along the ventral surface of the head 

 dividing it into .symmetrical halves; unless tho head is almost 

 completely exserted very, little of this groove can be seen. 



Close to the a,ntGro-latei'al borders of the mouth thei'e is on 

 each side a jore-o?'aZ sense organ (p.o.). In the majority of 

 (?yclorrha])hous la,rvae this organ lies anterior to the mouth 

 between the latter and the maxillary palps.; its lateral position 



