70 A BOOK OF INSECTS 



When present, the wings are exceedingly narrow, fringed 

 with long hairs on one or both margins ; but many species 

 are wingless. The newly hatched young resemble the 

 adults, save for the absence of wings ; but prior to the 

 last moult the nymph is sluggish, while in some cases it 

 actually becomes quiescent, and takes no food. Thrips 

 are probably world-wide in their distribution, but they 

 have scarcely been studied outside Europe and North 

 America. Perhaps the most common British species are 

 the pea and bean thrips ( Thrips pisivora) and the corn 

 thrips (Thrips cercalium). 



Order X. — Hemipteria. 



This large order includes the very numerous insects 

 which are known familiarly as " bugs," as well as cicadas, 

 aphides, and their allies. In all cases the mandibles and 

 first maxillae are needle-like piercing organs, while in con- 

 junction the mouth -parts form a suctorial apparatus. 

 The head is usually triangular in shape, while the antenna? 

 have from three to eight segments. There are two sub- 

 orders, viz. : — 



Sub-Order 1. — Heteroptera. 



These are the true bugs, in which the basal portion of 

 the fore-wing is leathery, although there is a transparent 

 area towards the apex, or tip. The hind-wings are en- 

 tirely membranous, and are folded on the back, beneath 

 the fore-wings, when the insect is at rest. A shield-like 

 plate, called the scutellum, is a prominent feature. It is 

 the dorsal part of the second thoracic ring (mesonotum), 

 and lies between the bases of the wings. The young 

 closely resemble their parents, save for the absence of 

 wings. This sub-order includes upwards of 10,000 known 



