REPORT OF THE SOCIETY 61 



Defoliating insects are controlled by spraying the infected foliage with lead 

 arsenate as soon as possible after the attack has commenced, or if the time can be 

 estimated, just before the eggs are hatched. 



The white-marked tussock moth is an excellent example of our defoliating 

 caterpillars, and an account of its control will be opportune at the present time, 

 since we are threatened with an outbreak of its caterpillars this coming summer. 

 The species is native to this country, and is found on deciduous trees nearly every- 

 where each season in varying numbers. In the Maritime Provinces and in the 

 region bordering on the St. Lawrence River and the Great Lakes its caterpillars 

 periodically become exceedingly numerous and are recognized as one of our most 

 serious shade tree pests. The last outbreak in Quebec Province ended in the sum- 

 mer of 191L The white-marked tussock is frequently injurious in orchards, 

 and destroys the young fruit in addition to defoliating the trees. 



Description of the Insect. 



The Adult. — ^The two sexes of the adult stage are strikingly different in 

 appearance. The male is a beautiful greyish moth, about an inch and a half 

 across the wings when spread, with tufted legs, feathered antennae, and trans- 

 verse wavy lines across the fore wings. 



The female, on the other hand, is a very stout and clumsy creature, greyish 

 in colour, almost without markings, and nearly wingless. She usually crawls 

 upon the cocoon from which she has emerged, and after pairing deposits there 

 her mass of eggs, and dies. 



The Eggs. — The eggs are deposited in masses containing from one hundred 

 to five or six hundred; one egg-mass is laid by each female, usually upon the 

 empty cocoon. The mass of eggs is covered by a thick layer of white frothy 

 fiuid which hardens rapidly, and, in addition to hoWing the eggs together, pro- 

 tects them from adverse weather conditions, and in some measure probably 

 from their enemies. The individual eggs are small, whitish, and nearly spherical. 

 The egg-masses of the closely related rusty tussock moth are laid bare upon 

 the cocoon, without the frothy covering, and are thus easily distinguished from 

 those of the White-marked Tussock. 



The Caterpillar. — The length, when full grown, is slightly more than an inch. 

 The colours are in longitudinal bands, more strongly marked behind, yellow below, 

 greyish on the sides, with a bright yellow, subdorsal band above on each side 

 of a median black band. The median dorsal line bears four prominent white or 

 yellowish brushes of hair, one on each of the first four abdominal segments, 

 and a small coral red tubercle on each of the sixth and seventh segments. The 



