THE ORDEES OF FLIES. 1 87 



of Gauze- winged Flies (Neuroptera), probably developed 

 directly out of the primaeval Flies, which differ from them 

 only by their perfect series of transformations. Among them 

 are the gauze-flies (Planipennia), caddis-flies (Phryganida), 

 and fan-flies (Strepsiptera). Fossil Flies, which form 

 the transition from the primaeval Flies (Libellula) to 

 the gauze-winged (Sialidse), are found even in coal 

 (Dictyophylebia). 



The order of Straight-winged Flies (Orthoptera) de- 

 veloped at an early period out of another branch of the 

 primaeval Flies by differentiation of the two pairs of 

 wings. This division is composed of one group with a 

 great variety of forms — cockroaches, grasshoppers, crickets, 

 etc. (XJlonata) — and of a smaller group consisting only of 

 the well-known earwigs (Labidura), which are character- 

 ised by nippers at the hinder end of their bodies. Fossil 

 remains of cockroaches, as well as of crickets and grass- 

 hoppers, have been found in coal. 



Fossil remains of the fourth order of Biting Flies, 

 beetles (Coleoptera) likewise occur in coal. This extremely 

 comprehensive order — the favourite one of amateurs and 

 collectors — shows more clearly than any other what 

 infinite variety of forms can be developed externally 

 by adaptation to difierent conditions of life, without the 

 internal structure and the original form of the body being 

 in any way essentially changed. Beetles have probably 

 developed out of a branch of the straight-winged Flies, 

 from which they differ only in their transformations (larva, 

 pupa, etc.) 



The one order of Licking Flies, namely, the iateresting 



