24 NEW YORK STATE MUSEUM 
If the place from which a cocoon has been removed is ex- 
amined, there are found two slits near one end [p1.30, fig.6css] 
and a circular excavation near the center which penetrates 
through the cocoon into the tissues of the plant [pl.30, fig.60h]. 
These slits were undoubtedly made by the caudal setae, as the 
openings are of the same Size as the setae and the same dis- 
tance apart and I believe it is the place where the larva was 
attached for the purpose of respiration while it was spinning 
its cocoon. Though numerous underground stems containing 
larvae were examined, yet I have never found a larva in the act 
of spinning its cocoon nor opened a cocoon with a larva with 
its caudal setae inserted in the slits. In every cocoon examined 
containing larvae except one, the caudal setae were in the oppo- 
site end of the cocoon from the slits, and in those cocoons con- 
taining pupae, the cast larval skins were in the opposite end 
of the cocoon from the slits. The only other way in which the 
slits could have possibly teen made was by the mandibles, but, 
when they are studied and their weak structure and their short- 
ness are noted, the impossibility of this explanation is appar- 
ent, and one is forced to the conclusion that there is no way 
that the slits could have been made other than by the caudal 
spines, and that the larvae must turn around in their cocoons 
after its completion and kefore shedding their last larval skin. 
In the case of the single exception noted the larva had prob- 
ably completed its cocoon and had not yet turned around. The 
cocoons are usually larger than the inclosed larva, so that there 
would be room for it to turn around if it so desired. In the 
cocoons of Donacia aequalis and Haemonia nig- 
ricornis the circular excavation near the center of the bot- 
tom of the cocoon is wanting, and the pupa has to depend en- 
tirely on the air that can reach it through the paired slits. 
Not only is the attachment of the larvae at the time they are 
Spinning their cocoons important for furnishing an adequate 
supply of air for the larvae while they are undergoing the great- 
est muscular activity of their life, but an abundant supply of 
air is also undoubtedly important in freeing their cocoons of 
water. If, when the cocoon was completed, it were filled with 
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