20 BULLETIN 1238, U. S. DEPARTMENT OF AGRICULTURE 



than two weeks; one lived 32 days, and the average length of life- 

 was 27 days. Practically all eggs were laid during the first few 

 days of confinement, and after this the moths were very sluggish and 

 inactive. Under field conditions, the moths doubtless perish in a 

 shorter time. 



Males of a known date of emergence were not available, but those 

 captured in the field and confined with the moths noted in Table 8 

 lived almost as long as the females, although it would hardly seem 

 likely that the fragile-winged males would survive long under field 

 conditions. 



SPEING EMERGENCE. 



It has been frequently recorded that the emergence of a few of the 

 moths is often delayed until early spring. On March 26, 1920, one 

 or two days after the frost had left the ground, a female moth, 

 evidently recently emerged, was found in an orchard near the 

 Wallingford laboratory. None emerged from the soil cages. 



SPRING CANKERWORM. 



DESCRIPTIONS. 



EGG. 



The eggs (PI. Ill, A) are laid in crevices in the bark of the tree 

 in loose clusters varying in number from a very few to more than 

 100. Quaintance (3&) reported the number as varying from 17 to 

 119, with an average for 12 masses of 47. Counts by the present 

 writers of '27 egg clusters, some of them laid in captivity and others 

 collected in the field, showed a maximum of 75 eggs to the cluster, 

 a minimum of 14, and an average of 34.5. 



The egg cluster has no definite form, and the eggs may be either 

 scattered or placed in a loose heap, somewhat stuck to each other 

 and to the surface next to which they have been placed. 



The individual egg is broadly oval in shape, one end being somewhat more 

 broadly rounded than the other. The length varies from 0.66 to 0.85 milli- 

 meter, with an average of 0.77 millimeter ; the width varies from 0.39 to 

 0.50 millimeter, averaging 0.45 millimeter. When first laid, the egg is a 

 shining white, but in a few hours turns a light pearly yellowish brown with 

 an iridescence giving purple and green reflections. The eggshell is thin with 

 minutely sculptured longitudinal ridges. 



First stage. — Width of head 0.25 to 0.28 millimeter, average 0.27 millimeter ; 

 length when newly hatched about 1.5 millimeters, when full-fed about 3.5 

 millimeters. General color dark olive green to black ; head dull dark brown 

 to black ; dorsum with a central longitudinal interrupted dull white line, 

 divided in the middle by a narrow, broken, olive-green line; each side with a 

 lateral dull white line. Venter brownish olive-green ; thoracic legs pale ; pro- 

 legs, which are present on the sixth and anal segments, pale. Tubercles pale, 

 tipped with darker color. Seta? short, pale yellow to white. 



Second stage. — Width of head 0.41 to 0.50 millimeter, average 0.45 milli- 

 meter ; length when full fed 5.5 to 6.5 millimeters. General color dark brown- 

 ish olive-green, practically black in most cases ; head dull black, whitish across 

 clypeus, with additional light markings which vary from white to pale brown: 

 dorsal surface with a median pair of narrow, broken, irregular white lines 

 separated by a median olive-green line : along each side is a fairly broad, dull 

 white line, more or less dotted with darker spots; between the lateral and 

 dorsal lines just noted are sometimes faint suggestions of one or two narrow 



