THE INSECT RECORD FOR I902 75 



During recent years the Fall Webworm 1 has been doing an 

 increasing injury to a great variety of fruit and shade trees. 

 This season the injury has been even greater than last, a great 

 many trees having been entirely defoliated by the pest. The 

 attack upon ash trees was especially severe. 



During the last few years an increasing injury has been 

 done by the White Fly of greenhouses, 2 a tiny pest from a 

 warmer climate. In the college greenhouses these insects 

 have been destructive especially to crops of cucumbers and 

 tomatoes. A series of experiments made by us during the 

 summer showed that this insect may be controlled by the use 

 of hydrocyanic acid gas. A detailed record of these experi- 

 ments will be found in Bulletin ioo. 



Another pest which has been present in the state for several 

 years, but has not heretofore been reported as doing serious 

 damage is the Pear-tree Psylla. 3 Complaints of injury in 

 pear orchards have been received during the summer from 

 central New Hampshire. 



The adult pear psylla is a small, jumping louse about one- 

 tenth of an inch long. It has four nearly transparent wings? 

 and is reddish, with transverse dark stripes on the abdomen. 

 There are two distinct forms. The summer broods are much 

 lighter in color than the brood which passes through the win- 

 ter. This difference is so great that the two forms were con- 

 sidered distinct species until the life history was carefully 

 worked out by Professor M. V. Slingerland. 



The dark form passes through the winter in some sheltered 

 situation about the tree, such as beneath loose bark or in the 

 crevices between the branches. In early spring they come forth 

 from their hiding places and deposit their eggs about the buds 

 and on rough bark. These eggs are very small. When first de- 

 posited they are yellowish, but turn dark soon afterwards. 

 The eggs hatch in three or four weeks, the time depending 

 largely on weather conditions. The young psyllas, which 

 during their immature stages are called nymphs, crawl to the 

 stalks of the unfolding leaves, in which they insert their tiny 



^Hyphantria textor Harris. 

 ^Aleurodes sp. 

 *Psylla pyricola Foerst. 



