624 NEUROPTERA. 



PoDURiD^ Burmeister. The Spring-tails are the typical 

 Thysanura, as they differ more than Lepisnia and allies from 

 all other insects. The anal bristles, which are free in Lepisma, 

 are here united and bent beneath the bod}', forming the 

 "spring" by which they leap to a prodigious height for sucli 

 minute insects. The body is cylindrical, not flattened, and is 

 covered either with hairs or scales. The four or six-jointed 

 antennae are short and thick, and the ej'es are simple, usually 

 four to eight on each side. The mouth-parts are not well de- 

 veloped, though mostly present, the mandibles being small, 

 with minute teeth, and the maxillary palpi entirely wanting 

 (Gerstaecker), though Lubbock states that the "second pair 

 of maxilla3 [labium] are membranous and delicate." The pro- 

 thorax is small, convex, while the two hinder thoracic rings 

 are large and similar to each other. The legs are stout, with 

 tarsi consisting of but a single joint. The abdomen consists 

 of six, sometimes only three segments, with a long anal stylet 

 forming the forked tail, or " spring," beneath. (Gerstaecker.) 

 They are found in gardens, or hot-beds, on manure heaps in 

 winter, and on the snow ; they may also be seen leaping on the 

 surface of the water in quiet pools. According to Nicolet 

 these insects are very prolific, as he found 1360 eggs in a sin- 

 gle individual. The embryo is developed in twelve days. 

 They moult often, and at periods of fourteen days each. 



The intestinal canal consists in great part of a long and 

 voluminous chyle- making stomach, into the lower end of which 

 six free Malpighian tubes pour their contents. (Nicolet.) In 

 Papirius JSaundersii, as in many other apterous Articulata, the 

 testis is formed on the same type as the ovary. On each side 

 of the body is a simple tube opening into a triangular reser- 

 voir with its base in front. The nervous system of Smynthurus 

 consists, according to Nicolet, of four ganglia, with a double 

 connecting cord. Two of these ganglia occupy the head and 

 form the oesophageal collar. The two others consist of a tho- 

 racic and one abdominal ganglion. There are in Podura four 

 pairs of stigmata in the four basal rings of the abdomen. Next 

 to the two main tracheae are six pairs of rather long vesicles 

 united with them by loops. (Gerstaecker.) 



Lubbock states that in Smynthurus there are but two spira- 



