166 SHADE-TREES IN TOWNS AND CITIES 



of the insect's being epidemic in neighboring cities, the trees 

 of East Orange have been kept free from this pest by the 

 collection of the egg masses. This insect usually attacks the 

 elms, the lindens, the white maple, and the horse-chestnut. 



Gipsy Moth (Porthetria dispar Linn.). Closely related 

 to the tussock moth in its mode of development, but more 

 destructive of plant life than any other species of pest is the 

 gipsy moth. Its caterpillars thrive on an exceedingly large 

 number of plants. They eat without hesitation almost all 

 of our native trees and shrubs. It is a European insect, 

 which was introduced into the United States in 1869, by a 

 naturalist who imported it in the course of some experi- 

 ments on silkworms. 



The winter is passed in the egg condition. The egg 

 masses are rounded or oval clusters covered with yellowish 

 hair from the body of the female, giving them the appear- 

 ance of a small piece of sponge. They hatch during May 

 or early June. As a rule the caterpillars feed at night and 

 hide during the day. 



When ready to change to pupae the caterpillars are apt to 

 wander from their food, sometimes for a considerable dis- 

 tance. Transformation to pupae takes place during the 

 month of June. The moths appear in July. Both the male 

 and the female insects have wings ; but the female rarely 

 flies. Pairing then takes place and egg deposition begins. 

 The eggs then remain till the following spring, when they 

 hatch and the same life cycle is repeated. 



As in the case of the tussock moth, one of the most effec- 

 tive methods of keeping this pest under control is the care- 

 ful collection and burning of the conspicuous egg masses. 

 This can be done most effectively in the fall, during the 

 winter and early spring. Creosote oil applied to the egg 



