Collembola 167 



surfaces, or it may be of use for breathing. On the 

 fifth or the fourth abdominal segment is situated the 

 spring, which consists of a basal unpaired segment — 

 the manubrium, whereto the paired denies forming the 

 "fork" are attached; each dens bears at its tip a 

 mucro sometimes clawed (fig. 91 f) and sometimes 

 clubbed. The spring is usually carried tucked be- 

 neath the insect's body with its tip pointing for- 

 wards ; as the spring is released and straightened out 

 so that its tip points backwards, the creature leaps 

 into the air. A small appendage, the " catch," found 

 beneath the third abdominal segment in some genera, 

 is believed to keep the spring in place by holding 

 the end of the manubrium. The bodies of Spring- 

 tails are covered with simple and clubbed hairs, and 

 often with flattened scales (fig. 91 c) (3, 98, 99, lOO). 

 Habits. — Springtails live in concealed situations 

 beneath stones or the bark of trees, in moss or 

 damp earth ; several species live on the sea-shore. 

 A number of individuals of a species are usually 

 associated together. They feed on decaying vege- 

 table matter and on the organic particles contained 

 in the mould which they swallow. 



Three families of Collembola are recognised ; all 

 are probably of world-wide distribution. 



Smynthuridae. — The Smj/Nt/u/riJa; are characterised by their un- 

 sealed globular bodies, the various segments being partially fused 

 together. The feelers are elbowed, the long fourth segment form- 

 ing a flagellum ; sometimes this segment is ringed or imperfectly 

 jointed. A well-developed spring is present on the fifth abdominal 

 segment. Alone among springtails, the Smynthuridse possess a 

 tracheal system. A pair of air-holes on the head behind the feelers 

 — a most unusual situation in insects — lead to sets of tubes branch- 

 ing all over the body. Smynthurus (fig. 910) and Papirius are the 

 only two genera of the family. 



Entomobryidae. — The Entomobn/nla have the head pointing 

 downwards and the body elongate with clear segmentation. Scales 

 are present in some genera, absent in others. The feelers are not 

 elbowed, but in one genus {Tomocerus^ the third and fourth segments 



