THE FOUK-HOKNED CKKATOMIA. 



323 



length of five or six inches, but, when not in use, is coiled 

 like a watch-spring, and is almost entirely concealed be- 

 tween two large and thick feelers, under the head. 



Among the numerous insects that infest our noble elms, 

 the largest is a kind of Spliinx, which, from the four short 

 horns on the fore part of the back, I have named Ceratomia * 

 quadricomis (Fig. 148), or four-horned Ceratomia. On 



some trees these Sphinges exist in great numbers, and their 

 ravages then become very obvious ; while a few, though 

 capable of doing considerable injury, may escape notice 

 among; the thick foliage which constitutes their food, or will 

 only be betrayed by the copious and regularly formed pellets 

 of excrement beneath the trees. They are very abundant 

 during the months of July and August on the large elms 

 which surround the northern and eastern sides of the Com- 

 mon in Boston ; and towards the end of August, when they 

 descend from the trees for the purpose of going into the 

 ground, they may often be seen crawling in the Mall in 

 considerable numbers. These caterpillars (Fig. 149), at 

 this period of their existence, are about three inches and a 



* Ceratomia, derived from the Greek, means having horns on the shoulders, a 

 peculiarity which I have not observed in any other Sphinx. 



