ANATOMY OF THE GOUT-FLy OF lUHLEY. 787 



does not at present justify any generalization, it is. perhaps 

 possible that the absence of this n,ppenclnge may be a reliable 

 distinguishing character of Acalyptrate larva\ 



At the posterior border of the mouth is a small lightly 

 chitinized plate (I.) bearing two small rounded sense organs {l.p') 

 close to the median line and near the posterior end of the plate. 

 I tliink there can be no doubt that these sensory organs are the 

 labial palps said by Keilin (9) to be present in all cyclorrhaphous 

 iarvre which he has examined, though these are in many cases, 

 notably in certain carnivorous Anthomyid larva) (10), much more 

 prominent structures than they are in Chlorops. If this ter- 

 minology is correct the chitinized plate must be considered as a 

 Labium — the presence of which as a distinct sclerite in a cyclor- 

 rhaphous larva is of considerable interest. 



There are several small sense organs on the surface of the lead, 

 and their position is shown in text-fig. 2 (c.s.o.). Each is slightly 

 raised above the surface of the head and consists of a minute 

 rounded pit with an encircling chitinous rim. 



Body- Segments. 



There are twelve body-segments, three thoracic and nine 

 abdominal, the first thoracic and the last abdominal bearing 

 respectively the anterior and posterior spiracles. It is usual in 

 describing Cyclorrhaphous larvse to distinguish a segment, 

 " Newport's Segment," between the head and the first body- 

 segment, which " is usually invaginated within the first thoracic 

 segment, so that it cannot be seen except when the larva is 

 forcibly extended" (Lowne, p. 34). Lowne (p. 748) failed to find 

 this segment represented in the embryo, and I am unable to find 

 any morphological reason for considering it as other than the 

 invaginable anterior end of the first thoracic segment. 



The lines of junction of the body-segments are marked by 

 bands of minute chitinous denticles which completely encircle the 

 body. The bands are not continuous but are formed of short 

 separate series of denticles. The thoracic teeth are long and 

 narrow, pointed posterioi-ly, and attached by their broad base 

 anteriorly. Very rarely their apices are bifurcated (text-fig. 2 A). 

 The abdominal teeth (text-fig. 2 B) are considerably smaller and 

 approximately semicircular in shape with the flat side attached 

 anteriorly and the rounded apex projecting backwards. 



The dorsal surface of the first thoracic segment is completely 

 covered by the rows of chitinous teeth. Ventrally it has a broad 

 anterior band and a narrow posterior band leaving a narrow 

 tmnsverse area between the two which is free from teeth. The 

 second thoracic segment is very similar to the first in the arrange- 

 ment of the chitinous teeth. The third thoracic segment has a 

 broad band round its anterior border only. 



Keilin (9) drew attention to the presence on the thoracic 

 Segments of the great majority of Cyclorrhaphous larvte, of two 

 types of sense organs, both of which occur in the larva of 



