2 PROC. ENT. SOC. WASH., VOL. 24, NO. 1, JAN., 1922 



view, but drop to the ground when disturbed and are easily 

 lost sight of. They were all full grown at this date and on the 

 point of leaving their foodplant. A search for the larvae a 

 week or even a day later would have been futile. When full- 

 grown the larva wanders from the foodplant in search of a 

 suitable log or tree trunk in which to pupate. There they 

 sometimes find accidental holes or cracks to satisfy them, but 

 much more often they bore into the sound bark, chewing their 

 way with the mandibles and leaving the chips behind as tell- 

 tale evidence of their presence, an evidence quickly effaced by 

 rain or wind. About a quarter of an inch or more from the 

 surface the larva makes a snug chamber, lining it with silk. 

 Here it pupates a few days later, remaining as pupa all through 

 the summer and fall. 



Many larva were taken home for rearing and they were 

 observed boring their way laboriously into solid bark of Cork 

 Elm taken along for the purpose. Others were given the 

 ingenious, ready made pupation blocks covered with isinglass, 

 invented and employed by the economic workers of the Bureau 

 of Entomology in Dr. Quaintance's Division. The Rthmia 

 larva at once adopted these, thus saving themselves the hard 

 work of boring their own holes. They merely lined and closed 

 the small chambers with silk, pupating head outwards to enable 

 successful issue of the adult. 



On a sunny day late in October or early in November the 

 adults appear and copulate on the tree trunks, flying rather 

 sluggishly when disturbed. An effort was made to keep moths 

 over winter under various conditions, but it was unsuccessful. 

 All of them died within a few weeks without laying eggs. It is 

 probable that in nature the moths live over winter, at least 

 the females, and that they deposit their eggs on the foodplant 

 in the spring. The foodplant has only a very short season in 

 April and early May. Then it disappears and there is no 

 evidence of it above ground. If the eggs of macelhosiella are 

 laid on the foodplant, which is the most reasonable supposition, 

 then the adult female must hibernate until early spring. But 

 the possibility that the eggs may be laid in the fall on the 

 ground or on the tree trunk and that the young larvae go in 

 search of their foodplant when it appears in the spring is not 

 excluded by our present observation. 



However this may be, the active life of this insect is confined 

 to a very short larval period in early spring and to an adult 

 period of a few days in early winter during which copulation 

 takes place. Through the entire summer it remains inactive 

 as pupa within the bark and during the winter it hibernates 

 inactively as adult (or possibly as egg). The eggs were not 

 obtained and it is not definitely known where anil how they 

 are deposited. Dissection of the abdomen of several fertilized 



