250 , INSECTS INJURIOUS TO VEGETATION. 



caterpillars that had come to their growth, and gone through all 

 their transformations during the same summer. This, however, 

 in Massachusetts, is not a common occurrence ; for by far the 

 greater part of these insects appear at one time, and require a 

 year to complete their several changes. The full-grown cater- 

 pillar measures one inch and three quarters or more in length. It 

 is clothed with long hairs, which are sometimes black and some- 

 times brown on the back and forepart of the body, and of a 

 hghter brown color on the sides. The hairs, like those of the 

 other Arctias, grow in spreading clusters from warts, which are of 

 a yellowish color in this species. The body, when stripped of 

 the hairs, 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 over- 

 taken by the tide, and when escape becomes impossible, they roll 

 themselves up in a circular form, as is common with others of the 

 tribe, and abandon themselves 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 Sve 

 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 ap- 

 peared to others at a considerable distance. From the marshes 

 about Cambridge they were once, it is said, driven in great num- 

 bers, 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, following 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 in- 

 sects 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 



