perature by spinning a thin web. There is only one brood, the insect 

 passing- the winter in the chrysalis state, and emerging as a perfect 

 moth in July and August. The imagines have the wings of various 

 shades of chestnut or chocolate brown, with a general resemblance as 

 regards their pattern and system of markings, viz. : four or five trans- 

 verse lines of a darker shade than the ground color, one or two discal 

 dots and a square, oblong, or triangular mark of the same shade upon 

 the disc of the thorax. Common though the caterpillars are, the per- 

 fect insect is very rarely met with, and it is only by raising them in 

 confinement in large numbers that the species can be obtained for the 

 cabinet, or for purposes of closer study. My friend Mr. S. L. Elliot, 

 of this city, has been for the past three years devoting a large portion 

 of his time to the breeding of these insects, and it is to his labor and 

 observation that I am largely indebted for the substance of this paper. 

 The genus Datana is of rather wide distribution, occurring as far north 

 as Canada, southward to Texas, and west as far as the borders of 

 Nebraska. It appears, however, to thin out as we get towards our 

 northern boundary, and is by no means abundant in Texas, two species 

 only as yet having been reported from that State, while it certainly 

 does not occur west of the Rocky Mountains. At the time of the dis- 

 tinguished entomologist, Thaddeus Harris, whose work on the " Inju- 

 rious Insects of Massachusetts" was published in 1852, only one species 

 was described, but Harris says, "I have seen on the oak, the birch, 

 the black walnut and the hickory trees, swarms of caterpillars slighdy 

 differing from those described, but their postures and habits appeared 

 to be the same. Whether they were all different species, or only varie- 

 ties of the well-known species arising from difference of food, I have 

 not been able to ascertain. ' ' The doubt which naturally arose in Harris' 

 mind is now, through the careful investigations of Mr. Elliot and others, 

 set at rest, and no less than eleven species totally distinct from each 

 other, and bearing unmistakable characters peculiar to themselves, are 

 now known to us. Four of these were described by Grote and Rob- 

 inson about thirteen years since; one by Walker, one by Drury, and 

 one by Graef The remainder are new species, and are at present un- 

 described. One of these new species I desire to bring before you this 

 evening. I am quite aware that there are many entomologists who 

 will maintain that these varied forms are what, for the want of a better 

 term, they are pleased to call "varieties." and the statement that these 

 slight differences are due to the food-plant, or to some climatic or other 

 circumstances, will by no means surprise me. But such objections fall 

 to the ground in the light of Mr. Elliot's experiments, the caterpillars 

 being changed from one food-plant to another, losing none of their 

 characters, but producing from generation to generation the same iden- 

 tical form. And I maintain that however closely allied two or more 

 species may be, if they possess characters peculiar to them.selves, which 



