WIXGS OF COCKROACHES 



225 



contrary, very like little antennae ; in the unwinged females of 

 this genus they are concealed in a chink existing on the under- 

 surface of the apex of the body. 



The alar organs of Blattidae are of considerable interest from 

 several points of view. They exist in various conditions as 

 regards size and development, and in some forms are very large ; 

 each tegmen in some species of the genus Bldbera (Fig. 132) may 

 attain a length of nearly three inches ; in other cases wings and 

 tegmina are entirely absent, and various intermediate conditions 

 are found. In Fig. 121 we give a diagram of the tegrnen or front 

 wing, A, and the hind wing, B, to explain the principal nervures 

 and areas. The former are four in number, and, adopting 

 Brunner's nomenclature * for 



a 



them, are named proceeding 

 from before' backwards medi- 

 astinal, a ; radial, & ; infra- 

 median (or ulnar), c ; and 

 dividens, d. An adventitious 

 vein, vena spuria, existing in 

 the hind wings of certain genera 

 is marked sp in B. 



The vena dividens is of s f- : - 

 great importance, as it marks 

 off the anal or axillary field, 

 which in both tegmen and 

 wing has a different system of 

 minor veins from what obtains 

 in the rest of the organ; the veins FIG. 121. Diagram of tegmen, A, and 



being in the anterior region wing B , in Blattidae. Nervures :, medi- 



astinal ; o, radial ; c, ulnar or infra- 



ablindantly branchingand dicho- median ; d, dividens ; sp, spuria. Areas : 

 /TT 1 ' 1 o r>\ i,'i 4-v. 1> mediastinal or marginal; 2. scapular 



tomous (Fig. 132), while in the o ; radial . 3> median . J ana i ^ axi ary 

 anal field there is but little 



furcation, though the nervures converge much at the base. The 

 mediastinal gives off minor veins towards the front only, the radial 

 gives off veinlets at first towards the front, but nearer the tip 

 of the wings sends off minor veins both backwards and forwards. 

 The infra-median or ulnar vein is very variable ; it is frequently 



1 Prod. Orth. europ. 1882, p. 27, and Rev. Syst. Orthopt. 1892, p. 15. Unfortu- 

 nately de Saussure adopts a different nomenclature ; we have preferred Brunner's as 

 being more simple. 



VOL. V Q 



