WINGLESS EARWIGS 



205 



have the 



Chelidura 



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 

 organs of flight undeveloped. Fig. 105 rej)resents 

 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), 

 are seen in the shape of a plate which may 

 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 Anisolabis (No. 3); or they may look like short 



Fic. 105. Chdidura 

 dilatata, male. Pj-reuees. 



broad slips extending all 

 across the body, and mark- 

 ing off a piece frequently 

 called a scut ellum , but which 

 is really the mesonotum 

 (some species of Chelidura, 



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

 invisible) of apterous earwigs. 1, Chelidura STp.; i p 



2, Chelidura dilatata ; 3, Anisolabis vioesta ; may be nearly tree tCg- 



4. A. maritivia. a, First thoracic segment ; h, i^^i^a, SOmewhat 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. holivari. 



In the cases we are considering no analogous structures exist on 



