Nerve^winged or Lace-winged Insects 



695 



NERVE-WINGED OR LACE-WINGED INSECTS, OR DRAGON-FLIES AND THEIR RELATIVES. 



BY THE V.KV. TnEODOUI-: WOOD, F.i:,S. 



The Nerve-winged Insects owe their title to tlie peculiar cLaracter of their wings, the 

 horny veins which form the framework of those organs being multiplied and sub-divided 

 to such an extent that they assume the appearance of exceedingly delicate network. 



These insects fall naturally into two great group.'*, in one of which the chrysalis, or pupa, 

 is active, and continues to take food like the grub, while in the other it is passive and 

 helpless, like that of a butterfly or a moth. 



Prominent among the members of the first division are the Dragon-flies, which owe their 

 title partly to their extreme voracity, and partly to the fact that they feed entirely upon 

 living insects, which they pursue through the air. They are exceedingly swift of wing, and 

 may be seen hawking over ponds and streams on any fine day throughout the summer and 

 early autumn. 



The earlier part of their lives is spent in the water, in which the eggs are laid by the 

 parent insect. The grubs are usually of a dull grey or brownish-green colour, and are remark- 

 able for a curious organ known as the "nrask," 



which partly covers the lower surface of the :: • '~ 



head. This apparatus consists of two joints, 

 which fold upon one another, but can be ex- 

 tended at will, the one farthest from the head 

 terminating in a pair of large and powerful 

 jaws. When the grub perceives an insect- 

 victim, it swims cautiously beneath, and seizes 

 it by means of these jaws. The "mask" is 

 then folded, and the prisoner drawn down 

 within reach of the mandibles, by means of 

 which it is speedily devoured. 



The method of swimming practised by 

 the dragon-fly grub is also very curious. 

 Through the centre of the body runs a 

 longitudinal tube, terminating in a circular 

 orifice, closed by means of five tightly fitting 

 valves. These valves, which together form a 

 sharp spike when closed, can be separated at 

 W'ill. When the insect wishes to swim, it 

 fills the tube with water, and then squirts 

 the contents forcibly out, the result being 

 that it is driven swiftly forwards by the 

 reaction. 



The pupa of the dragon-fly is \ery much like the grub, with the exception that the 

 rudiments of the future wings may be seen on the back. 



About forty species of these insects are found in the British Islands, of which the Geeat 

 Dragon-fly is a well-known example. The body is 3 inches in length, while the extended 

 wings measure about 4 inches from tip to tip. In colour it is light rusty brown, with a 

 few pale markings. The " Horse-stixuer "—which is perfectly harmless, notwithstanding its 

 popular title— is also common, and may be recognised at once by its flat dull yellow body, 

 which becomes blue in the fully developed male. In the graceful and beautiful Demoiselle 

 the male is deep blue, with black patches on the wings, while the female is entirely green. 



Allied to these insects is the Common May-fly, popularly supposed to live for one day 

 only. As a matter of fact, however, it spends a couple of years in the grub and pupa states, 

 inhabiting burrows in the banks of ponds and streams. These burrows are curved, and have 



Photo btj W. F. Dando, F.Z.S.] [Itegcifs Park. 



DRAGOX-FLY. 



These insects are often known as " Hoise-stingers," although they do 

 not sting horses ; in fact, thej are perfectly harmless, except to insects 

 smaller and -weaker tlian themselves. 



