GENEEIC CHARACTERS OF LARV^ OF CULICID^ 63 



a matter of fact, the green colour, when present, depends 

 largely on the nature and stage of digestion of the intestinal 

 contents. Hence, under certain conditions, Meinert's state- 

 ment is correct, but it cannot be called coloration in the 

 strict sense of the word. 



Genus Corethra. — The species examined by Meinert 

 were C. phwiicornis, and C. pallida. The larva; of this 

 genus differ markedly from those that have been already 

 described, and resemble those of the Ghironomidcc rather 

 than any of the CulicidcB. These larvaj are well known 

 as favourite objects for microscopic demonstration of 

 " pond organisms," and are generally known as "glass " or 

 "crystalline" larvae on account of their extreme trans- 

 parency, which is broken only by the four darker, but 

 still transparent, air sacs placed in the mesothoracic and 

 seventh abdominal segments respectively. The head is 

 much smaller than in any of the preceding genera, being 

 narrower than any other part of the body, except the last 

 two abdominal segments. Its hinder half is bounded by 

 straight parallel sides, as seen from above, but is contracted 

 in front, so that as a whole it presents the outline of a 

 broad-nibbed pen. The eyes are small and round, and are 

 placed well back on the head, rather on the dorsal aspect 

 of their sides, and behind each of the large eyes is a single 

 separate ocellus. 



The antennae are articulated, as it were, at the point of 

 the pen and are relatively small. Each consists of a single 

 joint with a constriction, followed by a small node just 

 beyond the base, and is armed at the end with five large 

 bristles, which spread out like the claws of a lizard. 



The tergum of the third metamere is rudimentary, but 

 its ventral plate forms the greater portion of the under sur- 

 face of the point of the pen, and is provided about its middle 

 with a sort of tubercle, from which radiate five pairs of 

 large bristles, while behind this are a pair of peculiar fan- 

 like plates, the posterior border of which is fringed with 

 fine hairs. The ventral plate of the second metamere is 

 generally spoken of as the labrum. It forms a sort of 

 ridge in the middle, and is provided with a number of 

 flattened hairs ; on either side are a pair of projections 



