112 'New York State Cotlege uf Forestry ' . 



breed on birch, but alder is by far the most common and the pre- 

 ferred food-plant of these species. 



Distribution: C. paUipes is a transcontinental species and 

 probably occurs throughout the northern part of the United States 

 and southern Canada. Specimens are at hand from New York, 

 Massachusetts, Maine, New Hampshire, Connecticut, Michigan, Wis- 

 consin, Oregon, Washington and Canada (Ottawa and Manitoba). 



Variation: Like a number of its congeners, paUipcs shows con- 

 siderable variation in size, shape of the hood, and also in the 

 relative proportion of the height of the crest of the hood with the 

 height of the median carina. There is also a moderate degree of 

 variation in size and general color of the entire insect. This 

 variation accounts largely for the synonomy of the species. The 

 adult insect ranges from 3.5 mm. to 4.32 mm. long. In relation 

 to the median carina, the height of the crest of the hood varies 

 from about twice to approximately three times that of the median 

 carina. The posterior portion of the hood also varies considerably 

 in width. On the same food plant one can find the extremes of 

 variations as well as gradual gradations leading to all intermediate 

 forms. There seems to be no distinct varieties, but the most com- 

 mon form generally has the hood a little larger than the type 

 (paUipes). There is also a little variation in the height of the 

 lateral carina. 



Injury (Fig. 45) : This tingid occurs on the yellow birch trees 

 by the thousands and it is undoubtedly the most injurious leaf- 

 feeding insect upon the yellow birch tree in the vicinity of Cran- 

 berry Lake. Although large trees are frequently infested it seems 

 to prefer the younger trees and seedlings. During the summers 

 of 1917, 1918, 1919, and 1920 the insect has been especially abun- 

 dant in the vicinity of Barber Point. Numerous young birches 

 were so badly infested that the leaves were almost entirely dis- 

 colored by its feeding punctures. In fact, the discolored leaves 

 of badly infested trees by the last of July would attract one's 

 attention several j^ards away. Later, many of these leaves would 

 be almost entirely destroyed. Ironwood probably ranks next to 

 yellow birch as a preferred food-plant, but white birch and beech 

 are often badly infested. Mountain ash and the various species of 

 maples do not seem to attract the insect very frequently and never 

 in great numbers; in fact they are very rarely infested at all. 

 There are two generations a year in the Adirondacks, the second 

 generation hibernating as adults over the winter among the fallen 

 leaves on the ground. 



The adults and nymphs feed almost entirely on the under-side 

 of the leaves (Fig. 45). The .young nymphs, especially during the 

 first and second instars, feed largely in colonies, but they gradually 

 scatter during the older stages. The discoloration, caused by the 

 feeding of the insects, is very conspicuous on both sides of the 

 leaves (Fig. 45). In addition to these discolored and feeding 

 areas there are small blackish spots on the under-side of the leaves 

 where the faeces have been deposited. 



