INSECTA 



425 



Subclass ENDOPTERYGOTA 

 Order NEUROPTERA (Alder flies, lacewings, antlions) 

 Rather soft-bodied insects with biting mouth parts ; two similar pairs 

 of membranous wings held in a roof-like manner over the body when 

 at rest. The wings have a primitive type of venation, a distinguishing 

 feature being the ladder-like arrange- 

 ment of veins along the anterior 

 border. The abdomen is without 

 cerci. The larvae are invariably 

 carnivorous — campodeiform , with 

 biting or suctorial mouth parts. 

 Aquatic larvae usually possess ab- 

 dominal gills. 



The alder fly, Sialis, may be taken 

 as an example with an aquatic larva. 

 In June and July the adults fly rather 

 sluggishly in the neighbourhood of 

 water. They lay eggs in clusters on 

 grass blades and leaves overhanging 

 water, and the larvae on hatching fall 

 into the water. In this larva (Fig. 

 315), more than in any other, the 

 paired segmented tracheal gills on 

 the abdomen show^ a great resem- 

 blance to paired limbs. Pupation 

 takes place in the moist earth near 

 the water's edge. The larva of Sialis 

 differs from those of the majority of 

 Neuroptera in that its mouth parts 

 are of the biting type, whereas in 

 antlion larvae and the larvae of lace- 

 wings, etc., the mouth parts are 

 adapted for piercing the skin and sucking the juices of animal prey. 

 For this purpose, the points of the mandibles and maxillae are used 

 for piercing, and the mandibles, being grooved, form with the closely 

 fitting maxilla a tube up which the fluid is drawn. The carnivorous 

 habit of neuropterous larvae plays an important part in insect pest 

 control, for example, larvae of lacewing flies feed largely on aphides. 



Order MECOPTERA (Scorpion flies) 

 A small order of insects distinguished by their vertically directed and 

 elongated head capsule carrying the biting mouth parts at its end; 

 two pairs of similar wings with a simple venation in which a number 



Fig. 315. Larva of Sialis lutaria. 

 From Imms, after Lestage. 



