October, ’23] 
cutright: micromus life history 
453 
framework to support the inner, which is now constructed. The larva 
doubles or curls up and now spins an oval, much more closely meshed 
cocoon which may be placed either along the sides or in the center of 
the outer one. It will measure about 5 mm. in length by 2.5 mm. in 
width. The larva can be distinctly seen through both of these loose 
silken envelopes. Three to four hours will be used in spinning the outer 
case. Construction on the cocoon proper is slow and it is hard to tell 
exactly when work on it ceases. 
The silk is spun from the anus, the larva moving the tip of the abdomen 
hesitatingly back and forth, up and down, and changing the position of 
the body frequently. 
After two or three days in the cocoon the final larval moult takes place 
(see tables) and the pupa stage proper commences. The shriveled ex- 
uvium remains at the tip of the abdomen. 
The place of pupation has not been accurately determined. It is 
probable however that it rarely takes place on the plant on which the 
larvae have found their food. Two things lead me to believe this; first, 
though I have constantly looked for them in the field, that is on plants, 
I have never found the pupa. Second, several larvae in the third instar 
were placed on plants infested with aphids. When ready to pupate 
they left the plant and pupated under some card board that was used to 
support the base of the “chimney” cage. It is probable therefore that 
the larva pupates under clods, stones or refuse or possibly in the soil. 
The pupal periods for sixteen individuals are shown in Table I. The 
average length of time required by this group for transformation was four 
and a fourth days. 
In emerging the pupa works its way out through one end of the cocoon 
and through the outer envelope, the emergence of the adult taking place 
on the outside or within a few mm. of the cocoon. So loosely are the 
two envelopes woven that the path of emergence is hard to see. 
The adults are more active at dusk but may be seen flying in dense 
shade and on cloudy days. On bright days they are usually found rest¬ 
ing quietly on the undersides of leaves and are not easily disturbed. 
I have noted them as most abundant on herbaceous plants, such as 
rape, etc., and also on white pine infested with Dilachnus strobi. None 
have been observed feeding in the open. In the laboratory where adults 
were kept without food for several days feeding would take place during 
the day when aphids were given them. 
The adults are practically always found on or about aphid infested 
plants or trees. A few have been taken early in the morning on the 
