110 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Riley thus describes (in our Repoit on Forest Tree Insects, p. 125) the fully fed larva 

 received hy him from Cedar County, Iowa: 



''' Larva. — Head large, fully as wide as the body; jet black. Body uniformly thick, cylin- 

 drical. On mesothoracic segment a pair of long and slender, stitl', black spines, lilunt at the end. 

 nearh' as long as the body is thick. They stand erect, diverging a little, and arise from swollen 

 bases, connected 1)V a slight transverse ridge. On each succeeding segment there is a transverse 

 series of four small, shai-p, simple sj)ines, one or two sometimes ending in two spines: and low 

 down on each side, below the spiracles, are three large and a fourth minute short acute spine. 



'"There are on the hinder part of the back of most of the segments two small l)lack spines. 

 The spines become larger on the last three, especialh' the penultimate segment. Supraanal plate 

 large and tiat, rather rough, ending in two acute spines, with four smallei' spines on each side. 

 Al)dominal legs larger and l)road, with stiti' short hairs on the hinder and lower edge. 



"Prothorax unarmed, ])ut with a thickened conical plate. Body jet-black, with a doulile 

 dorsal ocher-yellow-brown line, a narrow subdorsal line, and two wavy lateral lines of the same 

 color. A median ventral ocher-brown band. Length, \-l mm." 



Food plants. — Oak of different species and, rarely, the birch and raspberry. 



Ilahits. — The prickls' caterpillars of this species, during certain years, as I have noticed at 

 Amherst, Mass., and at Providi-nce, as well as in Maine, so aliound as to nearly strip large oak 

 branches of their leaves, and it is perhaps the most destructive of all our caterpillars to the 

 foliage of the oak. The spines, if they happen to penetrate the skin, as Fitch and others have 

 observed, sting like nettles. This species, ]Mr. Riley informs me, is the more injurious in the 

 Northern States, while A. ctigi/ni is most destructive in the Southern. According to Riley, 

 Mr. Bassett has bred a small ichneumon fly (Lhaneria {BaneJitis) fiigifiva Say) from this cater- 

 pillar. Riley has also bred it froiu the larva of Anisotit stigma, CJlsiocampa sijJmtlea, as well as 

 other caterpillars. 



Mr. Lintner states that "the lai'ViV occur so alnindantly at Center as wholly to defoliate 

 numbers of the smaller oaks. On the 7th of July the female moths \vere seen to have commenced 

 the deposition of their eggs on the under side of oak leaves in patches often nearly covering the 

 entire surface. On the 11th of July some newly hatched larva' wei-e observed." (Ent. Contr. , 

 I, p. 58, footnote 1.) 



In 1882 this caterpillar was very destructive to oak forests in Pennsylvania. Professor 

 Claypole writes to the (Canadian Entomologist (X^^ p. 38): 



"I have seen hillsides that looked as if tire had passed over them in consequence of the 

 destruction of the foliage hy millions of this species. In the w'oods they could be found crawling 

 over almost every square foot of ground and lying dead by dozens in every pool of water. The 

 sound of their falling " frass," too, was like a slight shower of rain. Farmers tell me they have 

 never known them so abundant before within their recollection. Harris sa3-s this species lives 

 on the white and red oaks in Massachusetts. Here the white oaks were untouched and the red 

 oak is not abundant. The food of the caterpillars was almost exclusively the foliage of the l)lack 

 oak {Quercus tinctmia), the scarlet oak (Q. cocchica). and the l)ear or scrub oak {(^}. ilicifolla). 

 (See also American Naturalist, XVI, p. 914.)" 



It was also abundant in September of the same year in Sagadahoc and Cumberland counties. 

 Me., and in Rhode Island. 



In the season of 1882 F. Clarkson observed the destruction to oaks in Columbia County, 

 N. Y. '"The moths,"' he says, "pair in the grass under the oaks, verj- shortly after pupation, 

 and as the wings of the female are small in proportion to the size of her l)ody, she is unable to 

 make a very extended flight. The eggs, as discovered by me, were attached to the under side 

 of the leaves at the terminal twigs of all the branches nearest the ground, the branches at an 

 elevation of 12 or 15 feet not showing a single deposit." (Papilio, II, p. 189.) 



In Minnesota the caterpillar is regarded as the most common and injurious insect to oaka 

 in the State, white, scarlet, and scrub oaks being stripped of their foliage. '"I have seen," 

 says Lugger, "such caterpillars so numerous that the whole grountl in the forests was covered 



