Mycetobia, Ditomyia, and Symmerus. 39 
formed me that he had found a specimen of Symmerus annu- 
lata which had hatched in one of his breeding-jars. ‘* The 
larvee of this species,” he added in his letter, ‘ were boring 
in a piece of rotten elm wood. They are almost trans- 
parent and glassy in appearance, and, like those of Ditomyia, 
move very little and very slowly. The pupz wriggle in an 
almost snake-like manner when extracted from their habitat. 
Unfortunately I found that all the full-sized larvee had 
pupated. I have one larva preserved in spirit.” 
All the material Mr, Edwards could seud me consisted of 
an empty pupa with a moulted larval skin attached to it and 
the larva preserved in spirit, mentioned in his letter. 
This was, however, quite sufficient for the complete 
morphological study of this larva. 
The larva of Symmerus annulata (Pl. V. fig. 26) is 11 mm. 
in length; its last abdominal segment bears the posterior 
spiracles, but is without the dorsal paired prominences which 
are present in Ditomyia larve. ‘These two larvee are easily 
distinguished from one another by their colour and post- 
abdominal prominences, but they are quite similar in the 
detailed structure of almost all their organs, 
The antenne (PI. V. fig. 32), labrum (fig. 27), mandibles 
(fig. 31), maxille (fig. 29, m.v.), and labium (fig. 29, /.6.), 
with their palps (m.p., /.p.) have the same structure as those 
of Ditomyza larve. The differences in detail of these organs 
in these two larve are shown in the above-mentioned figures. 
We may mention only that in the maxillary palps of 
Symmerus larve we do not find the lateral sensory papilla 
which is well developed in Ditomyia larve (PI. IV. 
fig. 17, is.). The labium in Symmerus larve is more 
rounded. 
The thoracic and abdominal segments also bear the 
sensory hairs, and the remains of the thoracic legs are 
represented by three sensory hairs (fig. 30). 
The last abdominal segment is rounded, 
The respiratory system is peripneustic, with nine pairs of 
functional spiracles: one prothoracic and eight abdominal. 
The spiracles (figs. 33 & 34) are very ‘small, and their 
structure is similar to those of the first seven. pairs of 
abdominal spiracles of Ditomyia. 
Pup (fig. 28). Unfortunately I have only one empty 
skin of a pupa. I may mention, however, that the pro- 
thoracic horns are more elongated than in the pupa of 
Ditomyia, and that the thoracic segments bear a row of 
lateral short hooks, 
