WINGLESS EARWIGS 205 



nature, and forms a triangular plate at the base of each half of 

 the forceps. Between the branches of the forceps there is a per- 

 pendicular plate, the pygidium of Orthopterists, possibly the 

 unpaired terminal portion of the body seen in some embryos, and 

 called the telson. The pygidium is a separate sclerite, though 

 it looks as if it were only a portion of the large tenth dorsal 

 plate bent downwards, and in some descriptive works is errone- 

 ously described as being such. 



A very large number of species of Forficulidae have the 

 organs of flight undeveloped. Fig. 105 represents Cheliduru, 

 dilatata, an apterous form that is very com- 

 mon in the Eastern Pyrenees. The condition 

 of the meso- and meta-nota — the parts from 

 which the tegmina and wings are developed, 

 and to which they are attached when present 

 — is very remarkable in these forms, and 

 exhibits much variety. In Fig. 106 we 

 represent the conditions of these parts in 

 a few apterous forms. The tegmina or the 

 segment from which they are developed (h), 



o . t' J. N. ^ "Pig 105. ChclidiiTm 



are seen in the shape of a plate which may ^uatata, male. Pyrenees, 

 extend all across the middle and be undi- 

 vided (No. 4) ; in which case the appearance indicates entire 

 absence of the tegmina; these are, on the contrary, evidently present 

 in the form of slips grafted one to each side of the second thoracic 

 segment in AnisolaMs (No. 3); or they may look like short 



broad slips extending all 

 across the body, and mark- 

 ing off a piece frequently 

 called a scutellum, but which 

 is really the mesonotum 

 (some species of Chelidura, 



Fig. 106.— Tegmina and wings (visible in part or ^g No. 2) ; Or, again, they 

 invisible) of apterous earwigs. I, Chelidura sp.; ^ f ao iocy 



2, Ghdidura dilatata ; Z, AnisolaUs moesta ; may De nearly II ee ue^ 



4. A. maritima. a, First thoracic segment ; b, ^^ina, SOmCwhat similar to 

 second ; c, third ; d, basal portion of abdomen. . 



those of the winged forms ; 

 this is the case with some species of Chelidura, as represented 

 by No. 1. This last figure is taken from a species from the 

 Sierra Nevada, apparently undescribed, allied to C. lolivari. 



In the cases we are considering no analogous structures exist on 



