No.:487. NORTH AMERICAN DIGGER WASPS— FERNALD. 305 



subdiscoidal vein. The places where these recurrent veins unite with 

 the culiital vein var}^ as regards the cubital cells, not only in different 

 species but in different individuals of the same species. As a o-eneral 

 rule the tirst recurrent vein joins the cubital opposite some part of the 

 second cubital cell, though it sometimes unites with the cubital directly 

 opposite the junction of this with the second transverse cubital, in 

 which case it is spoken of as being interstitial with the latter vein. 

 Similarly the second recurrent vein usually joins the cubital some- 

 where on the inner half of the third cubital cell, though in Sphe.x 

 {Ammojjhila Authors) and Scellphron^ belonging to the other sub- 

 families of the Sphecida^, it unites with the cubital vein behind the 

 second cubital cell. The distance apart on the cubital vein of the 

 second transverse cubital and second recurrent veins as compared with 

 the distance apart of the second and third transverse cubitals on the 

 radial vein is frequenth" a useful comparison in diagnosis. 



The outer part of the wing is free from closed cells, but the cubital 

 and sul)discoidal veins extend into this portion somewhat, partially 

 separating the fourth cu])ital, second apical, and tirst apical cells. The 

 amount of development of these veins beyond the closed cells differs 

 in different species. (Plate VII, tig. T, and Plate VIII, fig. 9.) 



Along the outer portion of the 'hinder margin of the wing, on the 

 anal cell, is a fold known as the frenal fold, in which the frenal hooks 

 of the hind wing catch, so that the two wings may act together. 



Tlmd ic'nigs. — The more important features of the venation of the 

 hind wings are as follows: The radial vein varies somewhat in the angle 

 it makes in bending toward the apex just after leaving the costa. The 

 path of the transverse cubital vein also varies, it in some cases being a 

 nearly straight cross vein between the radial and cubital, while in others 

 it curves so as to practically unite the last-named veins in a regular 

 curve. Sometimes the portion of the cubital vein outside the trans- 

 verse cubital is developed to a greater or less degree, more often only 

 a dark shade is present in that place, and sometimes there is almost no 

 trace of it present. The discoidal vein wvaj have the cubital either 

 external to the junction of the median, cubital, and transverse median 

 veins or at their junction. The angle between the transverse median 

 and the median veins (whether less, equal to, or more than a right 

 angle measured internally) and the amount of curvature of the former 

 are sometimes of some distinctive value, as is also the presence and 

 amount of a slight backward curve near the middle of the cubital vein. 

 The posterior lobe of the wing which extends from the base to the 

 sinus is well developed and an axillar}^ vein besides two folds are 

 present. 



Tegulge. — The tegula is a small chitinous plate lying over the base 

 of the fore wing and separating it from the side of the mesothorax. 

 It is somewhat arched, frequently with slightl}^ reflexed edges, and is 

 often somewhat sericeous or pubescent, particularly near the middle. 



