CLASSIFICATION AND DESCRIPTION OF COMMON INSECTS 363 



States, is closely associated with the corn-root louse or aphid {Aphis 

 maidiradicis Forbes). Forbes has shown very interestingly how the 

 ants carry the eggs of this aphis into the underground galleries of their 

 nests on the approach of winter, tend them carefully, and in the spring 

 carry the young aphids to suitable weeds, transferring them later to the 

 corn plants. 



In the control of this aphid, therefore, the best method is to plow 

 and harrow in the autumn infested fields so as to break up the ants' 

 nests, to destroy the weeds that may serve as temporary food-plants, 

 and to practise crop rotation. 



NEAR RELATIVES OF INSECTS INJURIOUS TO PLANTS 

 AND ANIMALS 



Crustaceans, Arachnidans and Myriapods belong also to the 

 great Branch of Animals called the Arthropoda, hence are here termed 

 "near relatives" of insects. 



Class Crustacea 



Sow Bugs, PiU Bugs or Wood Lice. — Sow bugs cause considerable 

 injury both indoors and outdoors to young growing flower and vege- 

 table crops. They occur in dark moist conditions, near dwellings such 

 as cellars, outhouses; about walls, cisterns, water 

 barrels; under boards, stones and rubbish; in green- 

 houses and rockeries. They usually feed at night. 

 They are sometimes injurious in mushroom beds 

 and to the roots of strawberries. 



The eggs are laid in early summer. The in- 

 cubation period varies with the different species — 

 in Armadilliiim vulgar e Latr. about 70 days. The 

 young are carried in a pouch formed of modified 

 plates on the abdomen of the female. Other 

 species are PorcelUo IcBvis Latr., A. qtiadrifrons, 

 and Oniscus asellus Linn. They have seven pairs 

 of legs, and antennae which are 7-jointed (Fig. 240). 



Control. — Cleanliness about outhouses, potting houses, etc.; the 

 use of baits of sliced potatoes covered with a thin coating of Paris 

 green, or Paris green, sugar and flour (1:2:2), or of bran-Paris-green- 

 molasses-orange juice; sprinkling or spraying with kerosene emulsion; 



Fig. 240. — Por- 

 celUo loevis, a common 

 sow bug. {After 

 Essig.) 



