INSECTS AFKECTIN'G PARK AND WOODLAND TREES 



323 



anal fork black tippi'tl. Thoracic feet blackish, marked witii black. Hoily 

 unicolorous, immaculate, or the oran^^e spots of the next staj^e partly 

 present (another brood). 



4th stage. Head shining black, the front with four grooves and two 

 dents above the clypeus ; sutvires around the mouth brown; width 1.4 mm. 

 Thoracic feet large, pale olive, 

 marked with black ; abiiominal 

 ones small, on joints 6-1 1, 13, pale 

 green. Body smooth, irregularly 

 5-annulate, the creases like slight 

 folds ; shining blackish, olivaceous, 

 with a series of lateral pale orange 

 spots, distinct only centrally. The 

 spots are above the subventral fold 

 on annulates 2 and 3. 



Larvae vary in shade, some 

 are blacker than others, and the 

 orange spots vary in distinctness. 

 The larvae scratch the leaf with 

 their anal prongs and make a rasp- 

 ing sound. 



5th stage. Width of head 

 1. 4-1. 6 mm. As before, slaty 

 black, except the feet ; lateral 

 orange patches on joints 3-12; 

 the two median annulates have 

 somewhat corneous, dorsal, trans- 

 verse areas, shining, but concolor- 



nlarged ; (/=aduU, 

 8. 1:33) 



Fig. 62 Pteronusv 

 tioii ; «=l.irva much 

 enlarged. (After H 



ous with body. Feet all pale watery. Two days after molting the larvae 

 began to turn shining and livid and with a pale dorsal streak anteriorly and 

 entered the ground to spin their cocoons. 



The adult insect is brownish, black, marked with yellowish white and 

 measures about I3 inch in length. 



Life history. The first indications of the presence of these slugs on 

 willow, according to Dr Howard, is seen in peculiar blisterlike swellings on 

 the upper surface of the foliage, which sometimes give it a wavy or 

 crumpled appearance. Investigation shows that these swellings are occa- 

 sioned by the presence of oval, whitish eggs partially inserted in the under 

 surface of the leaf substance. Black spots and streaks appear about the 

 time hatching begins, four to eight days after oviposition, the effect of 



