HIGH SCHOOL ZOOLOGY. 213 



Palps ai-e absent, except in some low wingless forms — the 

 ITallophaga — which live on the young haire and downs of 

 mammals and birds, and have, consequently, biting mouth parts. 

 Tliey, with the Pediculidce, which live by sucking the blood of 

 animals, form the sub-order Apiera. But the absence of wings 

 is not confined to this sub-order, some of the plant-parasites 

 (sub-order PIiT/fophthires) being also wingless. This sub-order 

 includes the plant-lice, Aj^hidce, and the scale-insects, which are 

 so harmful to plants (especially those cultivated in the house)? 

 the juice of wliich they suck by means of the pi'oboscis. 



Among the better known forms of these parasites are the Phylloxera 

 vastatrix, which was carried from this continent to Europe, and has 

 there done enormous damage to the vineyards, chiefly by forming galls 

 on the rootlets of the \nnes, and the cochineal insect {Coccim cacti), a 

 scale-insect which lives on the prickly-pear cactus in Mexico, and 

 which is the source of carmine, one of the most valuable dyes of 

 conunerce. 



The bulk of the Hemiptera belong to the two remaining sub- 

 orders, the Homoptera, in which the wings are alike, and the 

 Ileteroptera, in wliich the anterior are pai-tly converted into 

 elytra. To the former belong the musical Cicadidce, the males 

 of which have a vocal apparatus on the under sui-face of the ab- 

 domen, and the Gicadellidce, which are much smaller forms but 

 include many more species. To the latter, belong the water- and 

 land-bugs, Hydrocores and Geocores. In accordance with their 

 aquatic life, the Hydrocores have one or more pairs of legs 

 modified for swimming, their habitual mode of locomotion 

 during the day, but their hind wings enable them to fly, which 

 they do chiefly at night. All of them are predaceous forms, 

 sucking the blood of fishes, Ephemerid larvtp, etc. ; they are 

 capable of inflicting a sting by means of their proboscis. The 

 body may be elongated (Ranatra), or flattened (Belosfoma), or 

 keeled for swimming on the back (Notonecta). The Geocores, 

 however, include many more species, partly living on animal, 

 partly on vegetable juices. Some have extremely long legs, by 



