Mycetobia, Ditomyia, and Symmerus, 37 
The head of the larva is completely free, though it may 
be retracted in the first thoracic segment. The antennie 
(Pl. IV. fig. 23) are very small and consist of a short 
basilar segment which bears sensory orgaus of three different 
shapes : “(L) the main bell-shaped (4.s.) sensory organ 
which is very common in dipterous larve, (2) one bi- 
articulated papilla (p.), and (8) five short cylindrical 
papillee. 
The labrum (fig. 15) shows on its anterior margin a 
brush composed of ordinary sete mixed with sensory hairs. 
Oneach of its latero-anterior corners it bears a bidental 
chitinous plate (d.), and on its ventral side a series of short 
spines and scales me two strongly chitinised plates (p./.). 
The mandibles (fig. 22) 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 sete which originates from. 
the internal basilar corner of the mandibles. 
The maxille (fig. 17). The basal part or cardo of the 
maxillze consists of soft and transparent chitin with a trans- 
verse brown band (¢.4.) and a sensory organ in the form 
of a small circular groove. The internal part of the 
maxillz (m.a.) is conical in ioe and bears a long sensory 
hair (s.h.). The maxillary palp (m p.) is very well developed 
and furnished with a series of sensory organs and some 
ordinary chitinous sete. 
The labium consists of a short chitinous plate terminating 
in two tridental processes. On the ventral side it bears two 
hemispherical palps (/.p.) of transparent chitin, each with 
three sensory papille. 
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 larve and are always in direct con- 
nection with imaginal dises 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 sete. The last abdominal segment differs from all 
the others in bearing the anus and a pair of dorsal pro- 
jections terminated by spiracles. 
The respiratory system of this larvee is peripneustic, 7. e. it 
is composed of nine pairs of functional spiracles (one pro- 
