THE snow-flea: description of the insect. 205 



Charles M. Nes, of York, Penn., writes to the Smithsonian Institu- 

 tion, that with the snow-fall of the 8th of January (about twelve inches) 

 there appeared myriads of " spring-tails," or Podicrce, samples of which 

 were inclosed, covering the surface of the snow to such an extent as en- 

 tirely to discolor it. The phenomenon extended over an area of country 

 two miles in length, and half a mile in width. In a later communica- 

 tion Mr. N. says: " They were in clusters, and where I gathered the speci- 

 mens, I had simply to take them up by handsful ; the snow was literally 

 covered. They still exist in great quantities on fences, bushes, stones, 

 etc., in the vicinity where they first fell. 



Dr. J. G. Morris, of Baltimore, also reports a similar appearance 

 about ten miles north of Baltimore, about the same time; and last sea- 

 son they were observed in numbers near Sandy Spring, Maryland. 



Description. 



The original description and comparisons are the following: 



Black or blue-black: legs and tail dull brown. 



Length, 0,08 inch. 



Body black, covered vvith a glaucous blue-black powder but slightly 

 adherent, and sparingly clothed with minute hairs; form cylindrical, 

 somewhat broader towards the tail. A/ifc/incE short and thick, longer 

 than the head. Legs above blackish, beneath dull brown and much 

 paler than the body. Tail of the same color with the venter, shortish, 

 glabrous on its inner or anterior surface, with minute hairs on the oppo- 

 site side; its fork brownish. 



Though found in the same situations as the European P. nivalis, ours 

 is a much darker colored species. Say's P. bicolor is a larger insect than 

 the one under consideration, and differs also in size and in the color of 

 the tail or spring. From the habits of the present species, we should infer 

 that it might be abundant in all the snow-clad regions of the northern 

 parts of this continent ; it may, therefore, prove to be identical with P. 

 humicola of Otho Fabricius {Fauna Grocn/aiidica) of which we are un- 

 able to refer to any but short and very unsatisfactory descriptions, which 

 do not coincide well with our insect ( Winter Insects of Eastern New 

 York, pp. 10-11). 



Other closely allied species of the genus having subsequently been 

 described, the above description would hardly suffice for its positive 

 identification. Its more detailed description by Dr. Packard is there- 

 fore given: 



Achorutes nivicola. Podura nivicola Fitch, Winter Insects, N. Y. 



Antennas four-jointed, short, thick, of nearly even width throughout; 

 first joint as long as thick, second and third both of the same length, 

 but second considerably thicker; fourth a little longer than third, ancl 

 but slightly thinner. Feet with a large claw arising from a small joint 

 of the usual form, with a long, slender, tenent hair arising near the claw. 

 The anal appendages appear to be really two-jointed, and consist of two 

 spine-like appendages, with a common base and hollow at basal half. 

 Just below their middle is a joint, with a very slightly marked suture 

 externally. They are borne on a broad triangular tergite (that of the 



