376 HOUSEHOLD INSECTS 



SPRING-TAILS 



The spring-tails are very small insects rarely coming 

 under the observation of any one but entomologists. 

 Occasionally, however, they occur in vast numbers over 

 limited areas so that, despite their small size, they become 

 very conspicuous. The author has seen thousands of 

 individuals of certain species on the surfaces of pools of 

 water in Texas. The water actually appeared black 

 from the presence of the countless bodies of these tiny 

 insects. One species, known as the snow-flea (Ackorutes 

 nivicola), is sometimes found in large numbers on the 

 snow toward spring. Occasionally, the individuals of this 

 species become so abundant in maple sugar-bushes that 

 they cause considerable annoyance by getting into the sap. 

 The spring-tails are widely distributed and occur at 

 various altitudes and under widely differing climatic 

 conditions. They seem, however, to agree in one char- 

 acteristic, namely, they all demand a certain amount of 

 moisture and seem unable to exist for any length of time 

 in dry situations. 



The name spring-tails. — These tiny insects possess 

 the capacity of leaping or springing suddenly and when 

 disturbed or alarmed will try to escape by a succession 

 of quick leaps. On the end of the abdomen is a tail-like 

 appendage forked toward the extremity. In the dead 

 insect this appendage extends straight backward from 

 the body ; but in the living insect it is bent forward under 

 the body, where it is apparently retained in position, in 

 some species, at least, by means of a catch projecting 

 from the under surface of the body near the anterior end 

 of the abdomen. The catch is not present in all species. 



