142 ZYGMmDM AND BOMBYCID^ 



"July 15th, 1842. On the last leaf of a branch of Ti'/ia Af/iertcana 

 found a swarm of these caterpillars just hatched. The eggs were laid 

 on the under side of the leaf, forming a broad patch an inch in 

 diameter. On the 23rd examined the swarm again ; the caterpillars 

 were a quarter of an inch long. The little black dorsal tufts were 

 visible, though small ; the other hairs thin and permitting the skin 

 and tubercles to be easily seen. The insects were all together, as 

 thick as possible, side by side on the lower surface of a leaf. They 

 had eaten all the parenchyma of the terminal leaves of the twig, 

 leaving only the veins and intervening reticulations. They had spun 

 a few threads, forming a very slight and hardly conspicuous web on 

 the leaves and twig, probably in moving about, and not for a shelter. 

 When first found these caterpillars were mistaken for Hyphaniria /extor, 

 a circumstance which tends to show that these species should stand 

 near each other in a natural arrangement. " 



This species is widely distributed through the Northern States, ap- 

 pearing on the wing in June and July. Its characteristic food plant, 

 and the one from which it takes its specific name is the Carya porcina, 

 though it it not exclusively confined to that tree. It is very closely 

 allied to a species from Costa Rica (undetermined) which is so 

 similar that at first sight it might be easily taken to be identical. The 

 latter is somewhat larger and paler ; the markings similar in position, 

 but the shape and disposition of the spots in the sub-marginal band is 

 different, the spots being distinctly cordate and less regular in their 

 distance from the outer margin. 



