64 
The Simplest Insects 
is dull black, with head, legs, and bases of the antennae rust-color.” Smyn- 
thurus aguaticus (Fig. 87) often occurs in great numbers on the surface of 
pools. The insects look like tiny black spots on the water surface, but a 
little observation soon reveals their 
lively character. 
The Poduridae and Entomobryidae 
are represented in North America by 
twelve and fourteen genera respeC' 
tively. • Many of the Podurids are 
covered with scales and are often 
prettily colored and patterned. The 
scales (Fig. 98) are very minute and 
bear many fine lines and cross-lines, 
regularly arranged. On this account 
Fig. 98. Fig. 99. they are much used as test objects 
^' I Murra7 SC greatfy°magnified n f* a ^' for microscopes, the quality of the 
Fig. 99.—The snow-flea, Achorutes nivicola. lens being determined by its capacity 
(After Folsom; much enlarged.) to reveal their extremely fine mark¬ 
ings. One of the most interesting Podurids is 
the snow-flea, Achorutes nivicola (Fig. 99),.which 
gathers in large numbers on the surface of snow 
in the late spring. Comstock says that the 
snow-flea is sometimes a pest where maple- 
sugar is made, the insects collecting in large 
quantities in the sap. 
An interesting representative of the Entomo¬ 
bryidae is the house springtail, Lepidocyrtus ameri- 
canus (Fig. 100), said by Marlatt to be “not 
infrequently found in dwellings in Washington.” 
It is about one-tenth of an inch long, silvery 
gray, with purple or violet markings. In Europe 
also one species of springtail is common in 
houses. As these insects live on decaying vege¬ 
table matter, they probably do no special harm 
in the house. They especially frequent rather moist places, and may often 
be found in window-plant boxes and conservatories. 
Fig. ioo. —The American 
springtail, Lepidocyrtus 
americanus , ventral aspect, 
showing spring folded un¬ 
derneath body. (After 
Howard and Marlatt; 
much enlarged.) 
