Packard.] 
INSECTS AS ARCHITECTS. 
305 
the ground, with a hole (e) at the base. Mr. Rathvon, 
who observed this fact, says that the pupae await in the 
upper end of these chambers their time of transformation 
into the winged state, and when about to come from the 
ground, move backwards down the tube to below the level 
of the earth as at d, “ and issuing forth from the orifice 
would attach themselves to the first object at hand, and 
undergo their transformations in the usual manner.” 
Many plant lice allied to the Aphis, by their punctures 
cause the adjacent parts of the leaf to curl over and conceal 
Fig. 235 . 
them, or even give rise to the true galls, as elaborate as 
those of the gall fly. A kind of Pemphigus forms on the 
sumac the irregular growth represented by figure 236 (after 
Riley). The cock’s-comb elm gall (Fig. 237, after-Riley) 
often occurs in great numbers on the leaves of the white elm. 
“By the end of June or the beginning,” says Mr. Walsh, 
“the gall becomes full of winged plant-lice, when the slit on 
the upper side of the leaf, through which the mother plant- 
louse built up the gall early in the spring, gapes open and 
20 17 
