THE FURCULA IN THE COLLEMBOLA. 
BY J. E. GUTHRIE. 
The Collembola or “ Spring-tails ” comprise a very 
interesting order of wingless insects, usually associated 
with the order Thysanura, and frequently placed in that 
order. 
These little insects are common under bark and stones 
and among loose debris, wherever they can find dark, 
moist hiding places. As they range from less than 1 to 
only about 4 millimeters in length, and are usually very 
agile, we seldom notice them when collecting unless we 
are looking especially for them. 
In Iowa, the Collembola have been but little studied as 
yet. I have taken at Ames about 18 species representing 
12 genera. The order, and, in fact, many of its species is 
of world-wide distribution. 
The wingless condition of the Collembola is usually 
regarded as primitive, and thus these insects acquire an 
interest as throwing light, possibly, upon conditions which 
obtained among ancestral insects. 
Imagine a wingless ancestor which had already become 
a hexapod, that is, had the three pairs of thoracic legs 
developed for ambulatory purposes as is the usual condi- 
tion in the group today. Picture to yourself the segments 
of the abdomen of this insect as each possessing a pair of 
jointed, leg-like appendages, such as we may still find in 
more or less modified form in many aquatic larvae and in 
the adults of some of the species of Thysanura proper. 
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