76 NOTES ON THE " SCOTS GRAY " MOSQUITO 



The sixth longitudinal ends at 56. 



The second, third, fourth and fifth are all connected by 

 cross veins at point 60, forming a slightly zigzag line somewhat, 

 clouded. 



The lower border of the wing is fringed by deep sword 

 shaped scales, in bands alternately dark and light in colour. 

 Each scale is inserted at regular intervals in a socket on the 

 wing border ; against these another row is set, about half their 

 length. These are crossed diagonally by a row of still shorter 

 ones. This confers on the fringing scales great strength and 

 elasticity. The field of the wing is much mottled by the irregular 

 distribution of parti-coloured brown and yellow scales. 



The Tracheal System 



is well developed. On the pro-thorax are two large spiracles of 

 an elongated shape. One is represented by fig. 33. The pres- 

 ure of the cover glass has rendered the opening much wider than 

 it is in nature. The inner edge is furnished with a row of hairs 

 like an eyelash to keep dust and minute animals from entering 

 the tube, and around the sides are muscles capable of widening 

 or closing the aperture. It is by the adjustment of this opening 

 that the song of the insect is produced. Internally wide tubes 

 proceed carrying air to all parts of the body. On the mesothorax 

 two more spiracles are placed. The tubes proceeding from 

 them divide and subdivide until they become exceedingly minute. 

 In fig. 30 is seen the network as it ramifies on the outside of the 

 stomach. The remarkable way in which they subdivide, as well 

 as the spiral structure of the tubes is clearly seen, if one is 

 broken across, the fibre uncoils, and may be drawn out like a 

 spiral spring. 



The Scales 



invest the outward portion of the body and appendages like a 

 species of cellular clothing. They are light and being only 

 inserted at their basal point, while fulfilling the part of 

 armour, yet they interfere little with their freedom of move- 

 ment. They are arranged on the wings and other parts of the 

 body like shingles on a house-roof, the base of one being 

 overlaid by the blade of another, the only exception is on the 

 back of the head, where they are set perpendicularly. The 



