Packard.] 
INSECTS AS ARCHITECTS. 
313 
The largest gall we have is made by the Cynips covjluens , 
found on the scrub oak. It sometimes attains a diameter 
of two inches. It begins to form as soon as the leaves 
unfold. It is at first green and pulpy and has a central 
kernel in which the maggot resides. When the gall is ripe 
the shell becomes hard and dry, and after the fly has es¬ 
caped, which occurs in June and again in October, the de¬ 
serted shell is often tenanted by wasps. Some galls, as the 
bedeguar of the rose, are covered wdth vegetable hairs, and 
the variety of form in others is very great. On the rasp¬ 
berry and blackberry, as well as the blueberry, occur differ¬ 
ent sorts of galls. All are the result of the sting of the 
female, which is thought by some to convey a poison jnto the 
wound, though it is a question whether the egg introduced 
by the sting or ovipositor does not act as an irritant body, 
causing an excessive flow of sap and accumulation of cells 
resulting in the formation of a tumor. 
Passing by the ichneumon flies, which after all have the 
best of it, as they are tenants of living homes, supplied with 
the choicest of food at no trouble and fig. 245 . 
expense to themselves, we come to the 
cuckoo flies. The Chrysis (Fig. 245) 
is not a true wasp, but is in some re¬ 
spects allied to it. Its integument is 
very hard and thick, and beautifully 
tinted with green and blue and vari¬ 
ous metallic colors. When assailed Chrysis. 
it rolls itself into a ball, in the manner of a pill bug. Its 
sting is large and exceedingly painful, but not poisonous. 
The Chrysis is called a cuckoo fly, as it has the ichneumon 
trait of living at the expense of other insects. This fly 
may often be seen flying about posts and hollow stalks of 
plants, exploring the holes of wasps and bees, where they 
lay their eggs. The young hatch out some time after the 
larval bee or wasp, and then attack the latter, sucking its 
25 
