ARTHROPOD A 185 



the juices of roots until the seventeenth year, when they emerge, 

 moult and become adults. 



The plant lice or aphids {Aphididae) Include our most destructive 

 greenhouse and orchard pests. The grape phylloxeran {Phylloxera 

 vastatrix) causes decay of the roots of grapevines. Aphids undergo 

 parthenogenetic development. (See p. 123.) 



The scale insects, especially the San Jose scale, are extremely 

 injurious to fruits. The cottony-cushion-scale, which attacks the 

 orange groves of California, was successfully controlled by the lady 

 beetle ( Novius cardittalis) Imported from Australia. 



Several families of plant hoppers occur. These Include the 

 spittle Insects, the lantern flies, some of which are luminescent, the 

 leaf hoppers and the tree hoppers. The leaf hoppers are injurious 

 and difficult to control. 



Certain Hemiptera, known as the Parasitica {Anoplura), are 

 wingless and constitute formidable enemies of man and other mam- 

 mals. The species that Infest man (Genus — Pediculus) Include the 

 head louse, the body louse and the crab louse. Domestic animals are 

 infested by the genus Haematopinus. 



Order 12. Neuroptera. — A number of orders were formerly 

 grouped under the Neuroptera, but are now separated. The order 

 Neuroptera includes some very large Insects. They have four long 

 narrow and finely netted wings. Their metamorphosis is complete 

 and they have biting mouth parts. Their antennae are conspicuous. 



Larvae of the dobsonfly, known as " helgrammltes," are used for 

 fish bait. The a7it lions, or " doodle-bugs," make pits in sand, dust 

 or decayed wood, capturing thus many small insects. The adult 

 ant lion resembles a damsel fly. 



The lace-winged flies or " aphis lions" have thin lacy wings and 

 are green in color. Their larvae resemble those of the ant lions 

 but have yellow or red markings. They feed on colonies of plant 

 lice. The adults have brilliant golden eyes. 



Order 13. Mecoptera. — The scorpion flies have four membra- 

 nous wings, thickly veined but with few cross-veins. The head is 

 beaked and the mouth parts are adapted for biting. Metamorphosis 

 Is complete. Scorpion flies feed on small insects. Both the larvae 

 and the adults are carnivorous. 



Order 14. Trichoptera.—The caddice flies have rudimentary 

 mouth parts, four membranous wings thinly clothed with hairs, and 

 have complete metamorphosis. The aquatic larvae lack pro-legs 



