INJURIOUS INSECTS, FUNGOUS DISEASES, ETC. 175 

 SUCKING INSECTS 



Sucking insects eat no part of the plant itself, and it is 

 absolutely impossible for that reason to kill them with any 

 of the stomach poisons. They can be reached only by con- 

 tact poisons which act on the breathing pores of the insects. 

 Soaps and oils are the materials used, and these act by clog- 

 ging up the spiracles of the insects and choking them. 



Cottony Maple Scale {Pulvinaria innumerabilis Rathvon) . 

 — ^The cottony maple scale attacks all the maples to a cer- 

 tain extent, but is most injurious to the white maple. Dur- 

 ing the winter the hibernating females are found along the 

 underside of the twigs and branches. They are oval, brown 

 in color, and about one-sixteenth of an inch long. When the 

 sap starts to flow in the spring the insects begin to feed and 

 grow until they are about one-quarter inch long. In early 

 June they excrete a mass of white, waxy, or cottony material 

 in which the eggs are deposited. There are from one thou- 

 sand to two thousand eggs in each mass. The larvae hatch, 

 crawl up on the leaves and settle along the veins on the un- 

 der side. As many as a thousand settle on a single leaf and 

 suck the sap as it comes up through the veins. In the 

 meantime the waxy masses having served their purpose as a 

 protection for the eggs, disintegrate, and the bits of white 

 material are carried away by the winds. The pumping of 

 the sap by the growing larvae continues, the leaves become 

 devitalized and about the latter part of July the foliage be- 

 gins to fall as in late autumn. 



The insects go through two or three molts and then 

 change to pupae. The mature male insects are winged, the 

 female has no wings. In early September pairing takes 

 place, the males die, the impregnated females remain on the 



