148 
and perhaps useful in forming a sort of lever or brace when the 
larva needs the force to push and bite into the joints of its prey. 
The mother wasp does not feed her young from day to day, but 
stuffs a cell with beetles, lays her egg on one of the latter and 
closes the chamber. Consequently, when spinning time arrives 
some days later, the big grub finds itself surrounded by a debris 
of beetle fragments (for it devours only the tender interior), 
wing cases, antennae, legs, etc.; these, with an addition of grains 
of earth, compose a loose outer covering for her cocoon. It 
gathers up the fragments one by one and loosel y fastens them 
together with silk. In this framework the real, thin but opaque 
rich brown cocoon is spun. The head end of the cocoon (Fig. 
79) is quite the widest and the posterior extremity somewhat 
knobby. The smaller cocoons measure 24 x 6 mm. and the larger 
28x9 mm. In emerging, the wasp makes a couple of clean 
scissor-like cuts which free it at the broader end of its cocoon. 
My observations are from July to September, 1917. 
Sse, 
Ss > 

Fig. 80. Cerceris spiniger, 9, X 3.4. 
Cerceris spiniger Rohwer. 
Length 12 mm.; black, marked with yellow; wings fuscous on 
costa near apex; head remarkably broad. 
This species (Fig. 80), which I observed from June to August, 
1917, lives in the woods in small colonies, digging neat and 
steeply-inclined tunnels to a depth of about 16 inches in the rich 
soil. The soil which is brought up from below by the burrowing 
insect contrasts in color with that of the surface and is in part 
formed into a sort of short horizontal vestibule or half-tube lead- 
ing along the surface to the tunnel. One nest had two cells with 
long passageways, one cell being provisioned with nine small 
