THE CANADIAN ENTOMOLOGIST 75 



About 700 species of Collembola have been described so far, and of these 

 some 200 have been found in North America. But there are certainly a large 

 number to be discovered yet. Dr. Folsom estimates the collcmbolan fauna of 

 this continent at not less than 250 species.. 



They are all very small, delicate insects, ranging from one-half millimeter 

 to five millimeters in length, but the commonest kinds are from one to two 

 millimeters long. Their integument is very soft, and great care is necessary 

 in handling them. Most of them are clothed, thinly or densely, with hairs of a 

 remarkable variet>^ of form. There are long, slender, simple hairs, and stiff, 

 spiny bristles; there are wide, ribbon-like hairs, and hairs terminating in fancy 

 spear heads and in cups; there are hairs with flat, broad bases notched along one 

 edge; there are feathered hairs, clubbed hairs and hairs bent over sharply at 

 the ends. Of course, no one species possesses all these different kinds of hairs, 

 but most springtails can boast of three or four varieties at least. For con- 

 venience sake, we speak of these growths as hairs, but they have little in common 

 with the hairs of a mammal that grow out through the skin like an onion in a 

 garden bed. A springtail's hairs are really continuous outgrowths of the in- 

 tegument, and when the insect moults its skin, as it does frequently in the 

 course of its life, it sheds the outer layer of these so-called hairs also. 



A few genera are covered with scales, not unlike the scales on a butterfly's 

 wing, but very much smaller. These scales are lined and fluted so minutely 

 that they are often used as test objects for microscopes, and the exact nature 

 of the markings appears to be as hard to make out as the pattern on a diatom. 



In colour the Collembola run through the whole spectrum from red to 

 violet with black and white thrown in. Some are coloured uniformly all over, 

 some are irregularly blotched and spotted and some wear veritable Joseph's 

 coats of complicated symmetrical designs. Most of the colour is pigmentary, 

 but the scaled species often show beautiful iridescence. 



Some species are very constant in their coloration, while others assume 

 several different liveries according, it would seem, to their food or their habitat. 

 Thus Sminthuriis hortensis Fitch, taken on garden beds, is a very dark purple 

 with minute yelloAf spots, whereas a bright yellow variety, indistinguishable in 

 everything but colour, is found living in the adjacent grass. Achorutes armatus 

 Nic. may be a dirty white, pale violet, wine colour, or dark blue; and one 

 variety. Dr. Folsom says, is canary yellow mottled with lavender. The common 

 and abundant Podura aquatica, known all over the northern hemisphere, has 

 always been described from the time of I.inneus himself as dark blue with red 

 brown legs and antennae. But P. aquatica, recently found in the vicinity of 

 Arnprior, Ontario, is coloured uniformly red all over. Indeed, variations of this 

 kind are so common among the Collembola that colour is scarcely of any diag- 

 nostic value at all. 



The most striking feature of the Collembola is the leaping apparatus to 

 which they owe their popular name of Springtails. This apparatus is not 

 characteristic of all the Order, however, for there are a good many species 

 without any springing device at all, and in others it is so poorly developed as 

 to be inoperative; but the majority are active jumpers. The apparatus, which 

 i^ known as the furcula, consists of a forked appendage, (the dentes) hinged by 

 a broad base, (the manubrium), to the belly at the fourth abdominal segment, 



