244 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 



30. THE FALL WEB-WORM. 



Hyphantria cunea Drury. {R. textor Harris.) 



(Ravages, Plate xxxvi.) 



Passing the winter in the pupa state. The cocoons found during the winter prin- 

 cipally at the surface of the ground, mixed with dirt and rubbish, or in cracks and 

 crevices of tree-boxes, in fences, and under door-steps and basement walls. The first 

 moths issue from these cocoons in May, and laying their eggs in flat batches on the 

 under side of the leaves. The young worms feeding preferably in company, webbing 

 first one and then several leaves together, and gradually extending their sphere of 

 action until a large part of the tree becomes involved. The worms becoming full- 

 grown in July, and spinning cocoons from which a second generation of moths issues 

 early in August and lays eggs, from which the worms hatch, so they are once more in 

 force by the latter part of August. The parent moth white, with a varying number 

 of spots ; winged in both sexes ; the female preferring to oviposit on box-elder (Ne- 

 gundo aceroides), the poplars, cottonwoods, ashes, and willows. 



The following account is copied from Professor Riley's " Our Shade 

 Trees and their Insect Defoliators," as it contains the results of the 

 latest investigations : 



This insect has from time to time attracted general attention by its great injury to 

 both fruit and shade trees. Many authors have written about it, and consequently 

 it has received quite a number of different names. The popular name " Fall Web- 

 worm," first given to it by Harris, in his " Insects injurious to Vegetation," is suffi- 

 ciently appropriate as indicating the season when the webs are most numerous. 

 The term is, however, most expressive for the New England and other northern 

 States, where the insect is single-brooded, appearing there during August and Sep- 

 tember, while in more southern regions it is double-brooded. In our Third Missouri 

 Report we have first called attention to its double-broodeduess at St. Louis, and 

 we find that it is invariably two-brooded at Baltimore and Washington. Except in 

 seasons of extreme increase, however, the first brood does no widespread damage, 

 while the fall brood nearly always attracts attention. 



Limitation of broods. — At Washington we may say in general that the first brood 

 appears soon after the leaves have fully developed, and numerous webs can be found 

 about the first of June, while the second brood appears from the middle of July on 

 through August and September. In Massachusetts and other northern States the first 

 moths issue in June and July ; the caterpillars hatch from the last of June until the 

 middle of August, reach full growth and wander about seeking places for transforma- 

 tion from the end of August to the end of September. 



The species invariably hibernates in the chrysalis state within its cocoon, and the 

 issuing of the first brood of moths is, as a consequence, tolerably regular as to time, 

 i. e., they will be found issuing and flying slowly about during the evening, and 

 more particularly at night, during the whole month of May, the bulk of them early 

 or late in the month, according as the season may be early or late. They couple and 

 oviposit very soon after issuing, and in ordinary seasons we may safely count on the 

 bulk of the eggs being laid by the end of May. During the month of June the moths 

 become scarcer and the bulk of them have perished by the middle of that month, 

 while the webs of the caterpillars become more and more conspicuous. The second 

 brood of moths begins to appear in July, and its occurrence extends over a longer 

 period than is the case with the first or spring brood. The second brood of cater- 

 pillars may be found from the end of July to the end of September, hatching most 

 extensively, however, about the first of August. 



In Massachusetts and other northern States the first moths issue in June and July ; 

 the caterpillars hatch from the last of June until the middle of August, reach full 



