STRAW-COLOURED GNAT. 59 



we are now describing, however, has not been examined 

 minutely enough to determine the form of these organs. 

 It is of a light straw colour, and has two beautiful an- 

 tennae or feelers. 



The wings, also, of this gnat are of a delicate straw 

 colour, and make very beautiful objects, when mounted 

 under thin glass in sliders. Some species have their 

 wings marginated, and covered with fine scales. These, 

 as well as the feathers on the edges, are good objects for 

 the microscope, and exhibit five or six longitudinal lines 

 on each, which are so strongly marked as to be seen with 

 any kind of light, and do not require superior penetration 

 in the instrument, to shew them. The whole wing may 

 be seen very beautifully under Goring's improved Amician 

 Engiscope*, with its lowest power, which is equivalent to 

 a lens of a quarter of an inch focus. To the larva and 

 crysalis of insects this instrument cannot be applied satis- 

 factorily, as it does not take in the extent of field necessary 

 to shew the whole at once. On this account the achro- 

 matic microscope has the decided advantage, from the 

 low power and large area which can be obtained by it. 

 In examining this larva with the microscope, it will be 

 best seen when the light is thrown obliquely on it ; though, 

 when low powers are used, much attention to this parti- 

 cular is not required. 



These insects generate while hovering in the air, and 

 the female lays her eggs in the water, selecting an unfre- 



* See Micrographia, Chap. I. 



