INSECTS AFFECTING PARK AND WOODLAND TREES 157 



irregular slit at the middle of the epidermis and is at tiiat time a bluish- 

 gray color. The recently hatched larvae are uniformall)- curled up on the 

 underside of the leaf. The sawtlies become full grown in New York State 

 during the latter part of Jvily or in August, at which time they forsake the 

 leaves and spin a tough, coarse silken cocoon among the debris at tiie base 

 of the tree or just below the surface of the ground. The insects remain 

 unchanged in this shelter till spring when they pupate and the perfect fly 

 appears in May. 



Description. The egg when about to hatch has been described by Dr 

 Riley as oblong oval, somewhat flattened, and with a shell so thin and 

 pliable that it not only loses its regular shape with the slightest pressure, 

 but even by a slight movement of the embryo larva within. The shell is 

 perfectly clear and with no visible sculpture, except some fine, irregular 

 wrinkles and its surface is very sticky. At an earlier stage the egg is 

 elongate, nearly cylindric. The larva when full grown is about i,^^ inch 

 long, of a pale yellow color, with black eyes, a glaucous green body and 

 a black stripe along the middle of the back. The head is large, rounded 

 and is as wide as the body. The legs are pale whitish green and there are 

 8 pairs of prolegs. The abdomen is rolled up like a helix when the insect 

 is at rest and the segments are finely wrinkled and the ridges bear small 

 flattened w^arts [pi. i6, fig. 4]. 



The adult sawfly has a shining black head and thorax and her oval 

 body is of a steel blue or deep violet color, with 3 or 4 elongate oval yel- 

 lowish white spots on each side, which, in some specimens are much larger 

 than in others, and uniting within form continuous bands across the upper 

 side of the body. The antennae are short, knobbed, buff color, except the 

 basal segments which are dusky. The wings are semitransparent and smoky 

 brown in color. The legs are bluish black with yellowish tarsi [pi. 16, fig. 5]. 

 The male may be recognized by his more slender, longer body. 



Food plants. This species occurs more commonly on the willow and 

 elm in New York State. It has also been recorded on poplar by Dr 

 Lugger, and on alder by Dr Packard, who found it on that bush at Bruns- 



