CHAPTER IV 

 ORDER COLLEMBOLA* 



The Spring-tails 



The insects of this order are wingless insects still in a primitive condition. 

 The mouth-parts are formed either for chewing or for sticking. The adults 

 resemble the young in form for they do not have a marked metamorphosis. 

 The segments of the abdomen are reduced to six in number. On the ventral 

 side of the abdomen in many species is a springing organ. 



The spring-tails are minute insects, often of microscopic size and 

 rarely more than 1/5 of an inch in length. Most of the species live on 

 decaying matter. They are common under stones and decayed leaves 

 and wood, in the chinks and crevices of bark, among moss, and on 

 herbage in damp places. Sometimes they occur abundantly in winter 

 on the surface of snow where they appear as minute black specks which 

 spring away at our feet on either side. Some species collect in great 

 numbers on the surface of standing pools of water. 



There is, on the underside of the fourth 

 abdominal segment of most of these insects 

 a fork-like appendage, the springing organ 

 (Fig. 77), which, when the insect is at rest, is 

 bent forward beneath the body and caught 

 and held under tension by a catch on the third 

 segment. When this organ is released it sud- 

 denly springs-backward and throws the insect 

 high in the air several feet away. This action 

 is like a spring-board jump, only these tiny 

 insects always carry their spring-boards with 

 them, and thus have won the name of spring- 

 tails. 



Typically, the mouth-parts of the spring- 

 tails are chewing with the jaws overgrown by 

 the cheeks until they are hardly visible. In a few forms the 

 mandibles and maxillae have become modified into needle- 

 like organs which are used for piercing and sucking. 



These insects possess a peculiar organ called the ventral 

 tube, or collophore. It may be wart -like or tube-like in form and it is sit- 

 uated on the underside of the first abdominal segment. It exudes a 

 viscid fluid by means of which the insects are enabled to cling to the 

 lower surface of an object. 



A common species of spring-tail is the snow-flea, Achorutes nivicola 

 (Fig. 78), which occurs abundantly in winter on the surface of the snow. 



* Collembola: colla (n6\\a), glue; embolon (e^oXov), a bolt, bar; — from their 

 collophores. 



47 



Fig. 77. — The 

 "spring" of Papi- 

 rius: via. manu- 

 brium; d, left dens; 

 mu, left mucro. 

 (After Lubbock.) 



Fig. 78. — The 

 snow-flea, Achorutes 

 nivicola. (After Fol- 

 som.) 



