^fycetobin, Ditomyia, ati^I Symincru='. 37 



The head of the larva is-completely free, tlioiigli it may 

 be retracted in the first thoracic scjjjmeut. The antennae 

 (PI. I^^ fij;. 23) arc very small and consist of a sliort 

 basihir segment which bears sensory organs of three dilferent 

 sliapes : (1) the main bell-shaped {h.s.) sensory organ 

 which is very common in dipterous larvae, (2) one bi- 

 articiilated papilla (p.), and (3) five short cylindrical 

 papillae. 



The labrnm (fig. 15) shows on its anterior margin a 

 brush composed of ordinary sctte mixed with sensory hairs. 

 On each of its latero-anterior corners it bears a bidental 

 chitinous plate (//.), and on its ventral side a series of short 

 spines and scales and two strongly chitinised plates (p.l.). 



The mandibles (fig. 2,J) are very well developed, thick, 

 and of a dark brown chitin ; their external margin is slightly 

 cut into four teeth ; they bear three lateral sensory hairs 

 and a brush of ordinary brown setre which originates from 

 the internal basilar corner of the mandibles. 



The maxilhB (fig. 17). The basal part or cardo of the 

 maxilhe consists of soft and transparent chitin with a trans- 

 verse brown band (Lb.) and a sensory organ in the form 

 of a small circular groove. The internal part of the 

 maxillae {ni.x.) is conical in shape and bears a long sensorv 

 hair {s.h.). The maxillary palp {m p.) is very well developed 

 and furnished with a scries of sensory organs and some 

 ordinary chitinous setae. 



The labium consists of a slujrt chitinous pbite terminating 

 in two tridental processes. On the ventral side it bears two 

 hemispherical palps (l.p.) of transparent chitin, each with 

 three sensory papillae. 



The thorax is composed of three large segments furnished 

 with a series of sensory hairs. Among the latter we may 

 mention six groups of three hairs (fig. 19) which represent 

 the remains of the thoracic legs. As I have previously 

 shown (1911, 1915) these six groups of sensory organs 

 exist in all dipterous larvae and are always in direct con- 

 nection with imaginal discs of the thoracic legs. 



The eight abdominal segments bear also a series of sensory 

 hairs, and on their ventral side they are furnished with 

 lozenge-shaped projections or pseudopodia covered with very 

 short setae. The last abdominal segment differs from all 

 the others in bearing the anus and a pair of dorsal pro- 

 jections terminated l)y spiracles. 



The respiratory system of this larvie is peripneustic, ?. e. it 

 is composed of nine pairs of functional spiracles (one pro- 



