BV \V. R. COLLEDUE. 49 



beautiful epaulettes miiy be counted. The ladder-like structure 

 consists of the two tracheal or air tubes, which traverse the sides 

 of the body, while the cross bars are the dorsal plates. These 

 two air tubes terminate in the tail segment. In the culex they 

 project beyond the body. Here they are cut off flush with the 

 skin of the back, forming two circular apertures. These are 

 closed by valves when they descend so as to shut out the water. 

 Occasionally some obstruction gets into them and they bend like 

 a ring, and sweep the maxillary brushes across until the 

 obstruction is removed. 



The larva feed on organic forms attached to the stems and 

 leaves of aquatic plants. They can be seen industriously 

 sweeping their head brushes along and swallowing the product. 

 And I should think the hunter after diatoms might be rewarded 

 by finding some of these beautiful forms in the stomach and 

 intestines. 



They remain in the larval state much longer than the 

 ordinary variety, and likewise show the remarkable effect of cold 

 in retarding their development. During mid summer, the cycle 

 oi change from the deposition of the egg to the fledging of the 

 matured insect may occupy a month, but in cold ^veather double 

 that period is required. This is about three or four times longer 

 than the time occupied by the ordinary variety. This is 

 a great check upon the production of the insect in Queensland. 

 It so often chooses shallow pools for the reception of its eggs, 

 and these pools, under the dry winds and porous soils of our 

 colony, dry up long before the period of incubation is ended, so 

 that a very large portion of the insects die in the immature 

 state. The next slide represents a composite creature. I had 

 the good fortune to secure one of the larva passing into the pupa 

 stage (see Fig. 5). It has burst through the larval skin, and the 

 round projection on the shoulder is the head of the old larva, 

 whose skin partially invests the pupa. The tail, with its pro- 

 pelling setoe, and a number of those beautiful epaulettes, are 

 seen at the side. The next view (Fig. 6j is one of the pupa 

 entirely free. This is a lateral view of his lordsh.p. Attached 

 to the last segment of the abdomen are two broad flappers, which 

 are used to propel him through the water. From the sides of 

 the head arise two breathing tubes, or thoracic spiracles. They 

 project, and are thrust through the surface of the water for the 

 purpose of inhaling air, which is distributed by various tubes 

 through the body, and helps to develop the future mosquito. 

 Through the partially transparent case of the pupa may be 



D 



