622 NEUROPTERA. 



The two succeeding families were by Latreille placed in a 

 group by themselves (Thysanura), which was considered 

 equivalent to the Neuroptera, or Diptera, for example. More 

 recently they have been placed among the Neuroptera, though 

 Burmeister considered them as Orthopterous, by the close re- 

 semblance of the mouth-parts of Lepisma, especially the la- 

 bium, to those of the Bl attar ice. But in descending through 

 the last three families thysanurous characters have constantly 

 revealed themselves, as we have shown above, and the tran- 

 sition from some Sialidau, Hemerobid and Panorpid forms is 

 not so abrupt as it might seem. Indeed these low, apterous 

 insects stand in the same relation to the rest of the Neurop- 

 tera as the Flea does to the rest of the Diptera, or the Lice 

 and Thvips to the higher Hemiptera. In all these degraded 

 forms the metamorphosis is but slightly marked. The pupa 

 is active and closely resembles the larva, where in the higher 

 insects, such as the butterfly or bee, the pupa bears a close 

 resemblance to the adult, winged form. 



These interesting, minute, wingless forms, also afford a pas- 

 sage from the true winged insects to the Myriapods, by the uni- 

 form size of the rings of the bocty, which form a continuous 

 series from the head to the opposite extremity, as in the genus 

 Lepisma and allies, without showing the usual well marked 

 division into head, thorax and abdomen. Even the place of 

 abdominal legs is supplied in Lepisma by the rows of small 

 stylets which prop up the long slender abdomen. 



LEPISMATID.E Burmeister. Bristle-tails. These agile crea- 

 tures, which are revealed by turning over stones and sticks in 

 damp situations, and are often seen about houses, have a long 

 flattened body, with metallic scales, in form somewhat like 

 those of butterflies. The antennae are very long, setiform, 

 many-jointed ; the mouth-parts are free, with long palpi ; the 

 maxillary palpi being seven-jointed and the labial palpi four- 

 jointed. The mandibles are stout, sunken in the head, and 

 armed with teeth for gnawing. The prothorax is very large, 

 and all the rings of the body are of much the same size, so 

 that the insect bears a general resemblance to the Myriapods. 

 The anal stylets are long and large, which with the smaller 



