17 



The duration of the first generation observed was therefore thirty- 

 nine days. 



There is little doubt that in confinement a generation of this species 

 is produced which issues in April and May. The writer, therefore, feels 

 justified in considering the first generation reared at this office as the 

 second indoor one. Of the development of the first generation, then, 

 nothing can be said. 



A larva from the hypothetical first generation was observed to begin 

 the construction of its pupal case May 13, on the following day it spun 

 up and over night changed to pupa, the imago issuing during the night 

 of May 23, the duration of the pupal period for this individual having 

 been nine days. A second individual went through this process in the 

 same time, beginning to spin up May 16, completing its work the fol- 

 lowing day, being found as pupa next day and issuing as adult on the 

 27th; the weather was cool. In hot August weather the pupal condi- 

 tion consumed seven days. 



The midsummer generation, as observed at this office, ma}^ be passed 

 in thirty-four days; or, we may say, in about five weeks. The egg 

 state required but five days, and this with the pupa seven, leaves 

 twenty-two days or about three weeks for the larval period. 



In an exceptionally low temperature in which a midwinter generation 

 was reared under artificial conditions, neither that of a conservatory 

 nor the field, where the temperature varied from 42° to 62° F., eggs 

 laid January 19 hatched thirty-four days later, or in about five weeks. 

 The larval period was prolonged about two weeks, and the imagoes, 

 which laid the eggs in this experiment lived, some of them, a month, 

 and one for six weeks. 



The larva has been traced through its molts by Mr. Hine, at Colum- 

 bus, Ohio (1. c). In greenhouses he found that the larva makes its 

 first molt in eight days after hatching, and at intervals of about five 

 days thereafter, having four molts in all, the duration of the last stage — 

 that is, after the fourth molt — being about eight days. The duration 

 of these molts in a close conservatory in hot weather would, of course 

 be a day or two less. 



Two and probably more generations are unquestionably produced 

 annually in the open, and in hothouses a still greater number. At 

 least four are indicated for the average indoor temperature of a 

 conservatory. 



On this head, Mr. Hines says: " It is evident that at least five gen- 

 erations are produced in the interval between the middle of September 

 and the middle of the following May, or the time during which most 

 commercial greenhouses are in operation." 



Divisional records and those of captures show that moths have been 

 taken out of doors as early as April in central Illinois and central 

 Missouri, and in May in the District. Moths have been reared under 

 19288— No. 27—01 — -2 . ■ 



