14 
BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE. 
often some larvae, after feeding in a cluster of berries, will spin their 
cocoons and also pupate on the inside of one of them, or they may 
fasten their cocoons between the berries, mixing their silk with frass 
and any skeletonized leaves available. This is commonly true of the 
larvae of the second generation. It is not very unusual, therefore, to 
find some berries with the empty pupa cases protruding from a hole in 
the side. The great majority of the larvae of all generations, how- 
ever, descend to the ground to pupate. 
The Cocoon. 
As previously referred to, the cocoon of the blackhead fireworm is 
composed of strands of silk which the larva fastens to any surround- 
ing objects, as frass. leaves, or berries, and more or less loosely draws 
Fig. 0. — The blackhead fireworm : Typical cocoons formed out of dead cranberry leaves 
beneath the vines. The ones in the top row have been opened to show the interior ; 
those in the lower row show the empty pupa cases protruding. All slightly enlarged. 
about itself preparatory to pupation. The interior of the cocoon is 
shown in figures 6, 7, and 8. It is in cocoons similar to these that the 
larvae pass through a resting period followed by a final molting of 
the larval skin. This resting and molting, during which the pupa or 
chrysalis is formed, is called pupation. 
THE PUPA. 
The pupa or chrysalis of the fireworm is about 5.5 mm. or a little 
less than one- fourth inch long by 1.5 mm. or about one-sixteenth inch 
wide, and of a light amber yellow color immediately after casting the 
larval skin. This color soon changes to a deeper amber brown, and 
in pupae about to change to adults the color is a very deep amber 
approaching almost black The pupae are not usually encountered 
without a rather close examination of the leaves and trash beneath 
