THYSANOPTERA : THRIPS. 351) 



which the grasshopper rubs these nervures against each 

 other, produces a vibration in the membrane, and thus causes 

 the sound. 



In the family Locustidcs (comprising the locusts and grass- 

 hoppers with short antennae) the base of the wing-covers 

 (tegmina) of the males is not furnished with a circular spot 

 of membranous texture, and the chirruping noise which 

 they make is produced by rubbing the hind femora against 

 the margins of the wing-covers. These insects are exceed- 

 ingly active, leaping to great distances, and flying with equal 

 agility, and at considerable heights, feeding voraciously upon 

 vegetables, to which they are sometimes very destructive, and 

 amongst which the too renoAvned locust of the Scriptures 

 {Locusta wigratoria) is the most redoubtable. In this 

 country we possess about twenty-five species of this family, 

 but all of small size. 



ORDER IV. — THYSANOPTERA (Haliday). 



This order consists of the Linnaian genus Tkrips, com- 

 prising a considerable number of minute but very curious 

 insects, placed by Linnaeus in the order Hemiptera, by 

 Latreille in the Homoptera, but recently separated by Mr. 

 Haliday as a distinct order. The body is long, narrow, and 

 sub-depressed, resembling that of a Stophylinus ; the an- 

 tennae short, and composed of eight joints, the terminal joint 

 being unarmed Avith a seta ; the four wings are of equal size 

 and form, long and linear, deeply frmged with hairs on all 

 sides, and laid horizontally upon the back ; the tarsi are 

 short, and terminated by a vesicle instead of the ordinary 

 ungues ; the rostrum is described by Latreille as being small 

 or scarcely distinct, but the mouth is not rostrate, strictly 

 speaking, but armed with mandibles and pali)igerous maxillae, 

 and thus entirely differing from the other haustellated insects. 



