BRITISH FLIES 



37 



brown marks of the terminal dorsal segment diiferently placed to what they are in 

 ray specimens, but his tig. 80 is hardly consistent with his tig. 83 on this point. The 

 larva is said to l>e predaceous ; it lives under l>ark, and can be kept alive for months 

 without animal food. 



Fam. Tabanid-K (tig. 62). Head entirely invaginated. The rest of the body 

 consisting of twelve segments, the last of which is a short slender 

 tube so tliat the body appears pointed liehind, or even at both ends : 

 at the ai)ex of the terminal tul)e is placed the small spiracular 

 api)aratus : the l)ody is surrounded by pseud opods ; there is no pro- 

 thoracic spiracle, so that the larva is metapneustic. 



These larv:e are predaceous, eating small creatures either living 

 or dead ; they are usually aiiuatic or semia(|uatic. Tlie chief body 

 of information about them is Hart's account of the North American 

 forms, 1895. The various genera have a great family resemblance : 

 they are readily recognised by the (completely in- 

 vaginate head, the circles of pseudoi)ods, and the 

 small terminal breathing tube. The anus (placed 

 at the base of the eleventh body segment) 

 is accompanied by two large remarkable pro- 

 minences. 



Fam. Nemestrinid.e. Head very small, re- 

 tractile ; body-segments twelve. Posterior spiracles 

 terminal, well separated, placed in a transverse 

 fissure. Aniphi[>neustic. This family is not likely 

 to be found in Britain. The only known larva 

 lives inside the bodies of c()leo])terous insects in 

 their early stages. Only one or two naturalists have 

 been able to study it, and the above-mentioned 

 characters are gathered from Brauer. 



Fam. CYJtTlD.E (tig. 63). The larvae are parasitic 

 in. spiders. The head is very miimte, and the 

 posterior spiracles, according to Brauer, are accom- 

 panied by peculiar large plates. 

 Fam. BoMiiVLiiD.E (tig. 64). Larva ]iarasitic. Young larva consisting of a small 

 exserted head and twelve segments : elongate and slender : each thoracic segment 

 Avith a pair of long set;e : the penultimate segment 

 bearing two separated spiracles. When adult the 

 larva is very obese, has lost its long stiff bristles, 

 and looks very ditferent. The anterior part of the 

 pupa is armed with strong s])ines. The British 

 species of Bombj/lndce are probably all connected 

 Avith bees, but many of the foreign forms live at 

 the expense of insects of other Orders. 



Therevid.e. Elongate and slender, cylindrical, 

 consisting of a head and twenty segments ; head 

 moderately large, exserted. Amphipneustic. The 

 thoracic spiracle placed on the second l^ody- 

 segment ; the abdominal spiracle placed at the 

 side of the fourth segment from the apex ; the 

 terminal segment small. No pseudopods, but 

 there are a few fine bristles on the anterior three 

 segments. The increased number of segments is 

 supposed to be due to some of the true segments 

 being divided into two. Few larvai are knoA\n. 

 That ligured (fig. 65) was found by Mr Martineau 

 in decayed turnips. 



Fam. Scenopinid^. Larva like that of Thereva. 

 It has been found in houses, and it is still doubtful 

 whether it is predaceous or not. 



Fam. Mydaid.e. Larva said to be similar to 

 that of the rapacious Asilidce. 



Fam. Apioceeid^. Larva probably unknown. The one described by Brauer as 

 possibly belonging to the family is probably a Therevid. 



Fig. G3.— Youiiy lar\a 

 of Astomclla Lindenii. 

 [After Brauer 



Fig. 6-2.— 

 TabKnus citratus 

 larva. 

 [After Hart 



Fig. (ji. — Young larva and pupa of 

 Bomhyliui pumilus Niels. = minor L. 

 [After Nielsoii 



