THYSANOURA. 257 



Podura, Lin. 



These Insects are very small, soft and elongated, with an oval 

 head and two eyes, each composed of eight granules. Their legs 

 have but four distinct joints. The tail is soft, flexible, and formed 

 of an inferior piece, movable at base, to the extremity of which are 

 articulated two appendages susceptible of being approximated, se- 

 parated, or crossed they are the teeth of the fork. They have the 

 faculty of elevating their tail, and then forcing it suddenly against 

 the plane of position, as if they let go a spring, thus raising them- 

 selves into the air, and even leaping like the* Pulices but to a less 

 height. They usually fall on their back, with their tail extended 

 posteriorly. The middle of the venter exhibits a raised oval portion 

 divided by a slit. 



Some keep on trees and plants, under old pieces of bark, or stones; 

 others on the surface of stagnant waters, and sometimes on that of 

 snow during a thaw. Several unite in numerous societies on the 

 ground, and at a distance resemble little heaps of gunpowder. 

 Some species appear to propagate in winter. 



Poduiia, Lat. 



Antennae equal, and without annuli or little joints to the last seg- 

 ment; body nearly linear or cylindrical; trunk distinctly articulated; 

 abdomen narrow and oblong(l). 



Smynthurus, Lat. 



Antennae slenderer near the extremity, and terminated by an an- 

 nulated piece, or composed of little joints; trunk and abdomen united 

 in a globular or oval rnass(2). 



(1) Podura arborea, L. ; De Geer, Insect. VII, ii, 1 7; P- nivalis, L.; De 

 Geer, lb., 8 10; P. aquatica, L.; De Geer, lb., ii, 17; P. plumbea, L.; De 

 Geer, lb., iii, 1 4; P. ambulans, L.; De Geer, lb., 5 6; P. aquatica grisea, 

 De Geer, lb., ii, 18, 21. 



The Pod. vaga,villosa, cincta, annulata, pusilla, lignorum, Jimetaria, Fab. 



(2) Podura atra, L.; De Geer, lb., iii, 7 14; the Pod. viridis, polypoda, mi- 

 nuta, and signata, Fab. 



Vol. III. 2 H 



