INSECTS AFFECTING PARK AND WOODLAND TREES 527 



birch, willow, beech, plum and ironwood. The full grown caterpillar is 

 pale green shading into darker yellow, with yellow spiracles. There are 

 six rows of small, pink tubercles, each with one or more black hairs and a 

 few white hairs, some clavate, are scattered over the body. The anal shield 

 is brown, triangular, yellow-bordered and the anal plates are brown bordered 

 anteriorly with yellow. 



The adult, a magnificent light green, long-tailed moth with a wing 

 spread of about 4 inches, may be instantly recognized by reference to 

 plate 41, figure 2. 



Spiny oak worm 



A n z sot a st igm a H ii b n . 



A bright, tawny or orange-colored caterpillar with a dusky stripe along its back and 

 prominent spines on its thoracic segments, feeds on oak in September. 



This species is a rare one in the Northern States, though in the South 



it is frequently as destructive as our more common orange-striped oak 



worm, A. senatoria Hubn., to which it is closely related in structure 



and food habits. 



Slug caterpillars 



Peculiar, brightly colored, variously shaped and usually motionless sluglike caterpil- 

 lars occur in midsummer on the foliage of various deciduous trees. 



This group comprises a number of very interesting caterpillars remark- 

 able because of the apparent absence of legs and on account of their bril- 

 liant color in connection with a more or less well developed defensive armor. 

 These species vary widely in appearance, occur on a large number of trees 

 and shrubs and are very rarely abundant enough to be regarded as anything 

 more than natural curiosities. Some of these remarkable forms sting 

 severely and occasionally call attention to themselves in a very unpleasant 

 manner. It has been questioned some whether the sting is more than a 

 mechanical one due to the insertion in the flesh of multibarbed spines, and 

 in some instances, particularly with slug caterpillars, it would appear as if 

 such might be the case. Glands at the base of the spine have been 

 detected by European investigators who state that the hollow spines may 

 be filled with formic acid or a formate in solution. Still, careful investiga- 



