INSECTS affe(:ti.\(; park and woodland trees 319 



placed on end side by side in clusters on the untlcr surface of the leaf. 

 The nearly black L;rubs hatch ivom the e_<;-ij;s and feed for a short time in 

 company on the underside of the leaves, then separate more or less. The 

 young- grubs skeletonize the under surface of the foliage, and after increas- 

 ing in size, eat out ragged holes, 'i'hc grubs when alarmed, exude small 

 drops of a milky white fluid which can be withdrawn at the pleasure of the 

 insect. This process of expidsion and retraction may easily be observed by 

 alternately alarming the grulis ;ind allowing llnMii to remain quiet. They 

 also have a peculiar habit of elevating the abdomen and distending the anal 

 proleg when alarmed. The exudation above described and the threatening 

 movements are probabK' defensive means against native enemies. Pupa- 

 tion occurs in the partly cast larval skin which is firmly attached to the 

 leaves by the prolegs. The pupae are known to growers as " hangers," and 

 the adult beetles are called "hard shells." Professor Snow states that 15 

 days are required in August for this insect to pass through its immature 

 stages, thus indicating that in the W est, live broods may occur, though 

 most writers credit the species with only three or four. There are said to 

 be three annual generations of this insect in New York State, and it is very 

 probable that with the advance of the season, there is more or less over- 

 lapping of the broods. July 23, 1902, it was possible to tind all the stages 

 of the insect. There were few eggs, more recently hatched grubs, many 

 nearly full grown larvae, some pu])ae, and a few beetles. Adults, pupae 

 and older grubs belonged to the second generation and the eggs and 

 newly hatched larvae to the third. Most of the insects are said to dis- 

 appear from the willows about Aug. i. 



Food plants. This species, according to Dr Riley, has long been 

 known to feed on the leaves of different species of willows, and he states 

 that it is never abundant or injurious on these trees. He adds that it also 

 occurs on several species of Populus, and that its great liking for cotton- 

 wood appears to be a recent development. The species of willow suffering 

 most severely from this insect in New York State, is the osier or basket 

 willow of Europe. S a 1 i x v i m i n a lis. A German willow is also grown 



