ARTICULATA. 145 



Latreille in 1796, and considered a tribe of his order Gymnognatlm bj 

 Bunneister, the body is apterous, more or less cylindrical, and often covered 

 with minute scales like a silvery dust. The antenna are longer than the 

 liead, and the mouth is provided with mandibles and maxillae. They are of 

 active habits, living in woods, among moss, or beneath stones and bark. 

 Some of the small species are sometimes found on the surface of the water 

 near the margin, or hopping about on the surfiice of snow in winter, some- 

 times in great numbers. The order contains the two families, Poduridce 

 and Le^smidcB. 



Fam. 1 Poduridos,. Here the body is oblong or globular, the antennge 

 are rarely composed of more than four articulations, but in the genus 

 Maerotoma the three or four articulations are divided into a great many 

 rings or indistinct segments, indicating an affinity with the Lepismidse. 

 The palpi are indistinct according to some authors, and absent according to 

 others. The mandibles and maxillae are membranaceous, the eyes simple, 

 varying in number, and the abdomen is four or six articulate. The pro- 

 thorax is sometimes much reduced in size, or wanting above, although a 

 part of it remains below, to which the anterior feet are attached. Tlie 

 posterior extremity is provided with a spring or appendage bent along the 

 abdomen, and used in leaping. This, however, is wanting in the genus 

 Anura^ in which the mandibles and maxilltfi seem to be absent. They 

 are usually confined to damp places, and die very soon If deprived of 

 moisture. The oral aperture is so minute that it is supposed they subsist 

 upon the juices of decaying vegetable matter. 



Podura {pi. 77, jig. 79 «, natural size ; J, magnified, exhibiting the 

 caudal spring). Smynthurus {fig. 80) has the abdomen large and globular. 

 The species of this genus are often seen hopping upon the surface of water 

 and snow. The dark-colored species of this family are so abundant at 

 times as to give the snow the appearance of being sprinkled with course 

 gunpowder. J. M. M'Minii mentions their occurrence in the mountains of 

 Pennsylvania, in the following words (Proceed. Acad. Nat. Sci. iv, 246) : 

 " I have frequently noticed them in mid-winter on the snow, but I never 

 saw such a multitude of them together as I witnessed on the 17th of 

 Feb., 1849. The snow was entirely covered for the fourth of a mile along 

 the road, and several rods on either side. The mercury in Fahrenheit was 

 standing about fifteen degrees ; the atmosphere was dry and clear. These 

 little animals were quite stupid, and to all ap}>earance had been but a short 

 time there, and as it was about nine o'clock in the morning, I judged that 

 they arrived at night. Their motion was slow, and those on the top were 

 quietly endeavoring to get under. Tlie next day, when I again passed the 

 spot, I could not detect a vestige of them. The M^nd had been strong from 

 the north for several days, and I have noticed that we had strong north 

 winds whenever I had seen them.^^ Tliis species is probably the Podkirm 

 nivicola described by Dr, A. Fitch, who gives a similar history of it in his 

 account of the " Winter Insects of Eastern ISTew York," published in the 

 Am, Jour, of Agr. and Sci, for May, 1 847. 



Fam. 2, Lepismidce. In this family the antennae are setaceous, and 



349 



