82 ANIMAL BIOLOGY 



RECOGNITION-CHARACTERS FOR THE PRINCIPAL 

 ORDERS OF ADULT WINGED INSECTS 



(All are wingless when young, and wingless adult forms occur 

 in all the orders: order APTERA lacks wing-bearing thoracic 

 structures.) 



A single pair of wings is characteristic of the order DIPTERA. 



A jointed beak, that is sheath-like, inclosing the other mouth 

 parts, is characteristic of the order HEMIPTERA. 



A coiled sucking proboscis and a wing covering of dust-like 

 microscopic scales are characteristic of the order LEPIDOPTERA. 



Horny sheath-like fore wings, covering the hind wings and 

 meeting in a straight line down the middle of the back, will dis- 

 tinguish the order COLEOPTERA. 



Hind wings folded like a fan beneath the thickened and over- 

 lapping fore wings, will distinguish most members of the order 

 ORTHOPTERA. 



The possession of a sting (in females) and of two pairs of thin 

 membranous wings the small hind wing hooked to the rear mar- 

 gin of the fore wing will distinguish the common HYMENOPTERA. 



Besides these, there remain a number of groups most of which 

 have in the past been included under the order NEUROPTERA, 

 among which the Mayflies will be readily recognized by the lack 

 of mouth parts and by the possession of two or three long tails ; 

 the dragon flies by the two pairs of large wings, enormous eyes, and 

 minute bristle-like antennae ; the scorpion flies,. by the possession 

 of a rigid beak, with the mouth parts at its tip ; the caddis flies, 

 by their hairy wings and lack of jaws ; the lace wings, by the 

 exquisite regularity of the series of cross veins about the margin 

 of their wings, etc. 



