THE SALT-MARSH CATERPILLAR. 
353 
is yellow, shaded at the sides with black, and there is a 
blackish line extending along the top of the back. The 
breathing-holes are white, and very distinct even through 
the hairs. These caterpillars, when feeding on the marshes, 
are sometimes overtaken by the tide, and when escape be¬ 
comes impossible they roll themselves up in a circular form, 
as is common with others of the tribe, and abandon them¬ 
selves to their fate. The hairs on their bodies seem to have 
a repelling power, and prevent the water from wetting their 
skins, so that they float on the surface, and are often carried 
by the waves to distant places, where they are thrown on 
shore and left in winrows with the wash of the sea. After 
a little time, most of them recover from their half-drowned 
condition, and begin their depredations anew. In this way, 
these insects seem to have spread from the places where they 
first appeared to others at a considerable distance. 
From the marshes about Cambridge they were once, it is 
said, driven in great numbers by a high tide and strong wind 
upon Boston Neck, near to Roxbury line. Thence they seem 
to have migrated to the eastern side of the Neck, and, follow¬ 
ing the marshes to South Boston and Dorchester, they have 
spread in the course of time to those which border upon 
Neponset River and Quincy. How far they have extended 
north of Boston I have not been able to ascertain ; but I 
believe that they are occasionally found on all the marshes 
of Chelsea, Saugus, and Lynn. Although these insects do 
not seem ever entirely to have disappeared from places where 
they have once established themselves, they do not^ prevail 
every year in the same overwhelming swarms ; but their 
numbers are increased or lessened at irregular periods from 
causes which are not well understood. 
These caterpillars are produced from eggs, which are laid 
by the moths on the grass of the marshes about the middle 
of June, and are hatched in seven or eight days afterwards; 
and the number of eggs deposited by a single female is, on an 
average, about eight hundred. The moths themselves vary 
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