ARTHROI'ODA 



107 



Order I. Thysanura 



The Thysanura (Gr. dvaavos, tassel, and ovpd, tail) are the 

 lowest and simplest of the insects. They are lor the most part 

 minute, the largest only about eight millimeters long, the majority 

 much shorter. There are no wings on these insects at any stage 

 in their development; the month parts are rudimentary and 

 weak, and the abdomen some- 

 times bears rudimentary ap- 

 pendages. Further, there is 

 no metamorphosis in their 

 development, but the young 

 animal is like the adult. All 

 the facts point to the low- 

 organization of the Thysa- 

 nura, and they are particularly 

 interesting as affording a sort 

 of connecting link between 

 the more highly developed 

 Hexapoda and the Myriapoda. 

 Some of the commoner repre- 

 sentatives of the Thysanura 

 are the bristle tails and fish 

 moths ; they have rather long Fig. 193- Lephma. (After Guerin and Per- 



, . , . . , , cheron, trom Parker and Haswell's Text- 



bristles at the posterior end of book .) 

 the abdomen (Fig. 193), and 



are frequently seen in houses, libraries, and offices. The fish moth 

 is covered with minute, silvery scales like a fish, and feeds upon 

 starch, often injuring starched clothing and the binding of books 

 in this way. The spring tails also belong to this order, so 

 called because of a springlike appendage on the ventral side 

 of the abdomen by means of which they jump about; they are 

 common under stones and wood and sometimes on the surface 

 of quiet water. 



Order 2. Pseudoneuroptera 



The Pseudoneuroptera (Gr. ^eu&fc, false, and Neuroptera) 

 formerly constituted a single order with the Neuroptera, and it 

 will be noticed that in the more extended classification they are 



