96 NEUROPTERA. 



Thysanura. 



Wingless, mandibalate insects, with long many-jointed antennae; 

 abdomen composed of ten segments ; not undergoing metamor- 

 phoses, and not parasitic. 



This group (with which the CoUembola were formerly in- 

 cluded) is generally classed either as a distinct Order (perhaps not 

 truly belonging to the insects), or is treated as a degraded or 

 j)erhaps a primitive form of the Orthoptera or Neuroptera. Their 

 affinities are studied with great care and attention, because they 

 are supposed to represent some of the oldest forms of insects, and 

 it is thought that their study will throw light on many interesting 

 affinities between forms now widely separated Avhich might other- 

 wise be overlooked. The standard work on these groups is Sir 

 John Lubbock's " Monograph of the CoUembola and Thysanura" 

 published by the Ray Society in 1873. 



The Thysanura are generally known as " Springtails," from pos- 

 sessing two or three long caudal appendages. They are divided 

 into several families, of which the LeplsmatidcB are the best known. 

 Their bodies are covered with scales, while those of the other 

 families are only covered with hairs. Lepisma Saccharina, Linn., 

 which measures one-third of an inch in length, is a very common 

 species, frequenting dark dry places ; it is frequently found among 

 sugar-stores, between the cracks of boards, and sometimes among 

 stored books. It is called the " Silver- fish," from its silvery white 

 colour, and the manner in which it shoots or glides along when 

 disturbed. I once examined a chest of books carefully, among 

 which this creature was common, without being able to j)erceive 

 that the books had sustained the slightest injury ; but I have been 

 informed that the insect has caused great damage to a public 

 library at Malta. It is, however, quite possible that this library 

 was infested with several species of insects, and that the blame 

 was laid upon the Lepisma as being the largest and most con- 

 spicuous, while the real offenders escaped notice. The remaining 

 species of Lepismatidce are found under stones, under bark, or in 

 ants' nests; those of the genus Machilis, Latr., frequent damp 

 places, M. Mariiivia, Leach, being common on the sea-shore. It is 

 brown, rather larger than Lepisma, and instead of the three longest 

 anal appendages being of nearly equal length, the middle one is 

 more than twice as long as the lateral ones in Machilis. The 

 Camjwdeidce are furnished with two long caudal appendages, set 



