56 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



ing with the fossae (d) of the subcosta. The slender part posterior 

 to the condyle, which was called the scapular arm by Hopkins (k), 

 bears a hornlike process (1), the axillary horn. The horn forms with 

 the scapular arm an axilla (m) in which the anterior process (n) of 

 the second axillary rests. The margin towards the notum or articu- 

 latory margin (Hopkins) (o) is connected with the posterior prealar 

 process of the prescutum by the scapular hook (p) and tendons. The 

 scapular hook is a heavily chitinized hooklike plate on the lateral 

 margin of the prealar process. The margin towards the apex (q) of 

 the wing fits into the lateral groove (r) of the second axillary. The 

 base of the scapular plate is deeply emarginated. 



Second axillary. — The second axillary (fig. 30, axg) or subscapular 

 plate has the shape of an equilateral triangle with its base anteriorly. 

 The side towards the first axillary bears a deep groove, the lateral 

 groove (r), which encloses the apical margin of the first axillary (q). 

 With axillary four it is connected by a membrane only while a well 

 developed tendon (s) connects axillaries two and three on its pos- 

 terior end. By means of this tendon a strong connection is brought 

 about from the posterior prealar process to the first, second and third 

 axillaries. 



Third axillary. — The third axillary (fig. 30, axs) or flexor plate 

 (Hopkins) has the shape of a sickle with two emarginations (t, u) on 

 its inner side. The anterior one (t) ends in the tendon connecting 

 axillaries two and three. The handle of the sicklelike plate (v) is 

 without special characters. The blade (w) shows on its posterior 

 margin near the apex a membranous fold (i) connecting this plate with 

 the cubital vein. 



Fourth axillary. — The median plate (Hopkins) corresponds to the 

 fourth axillary (fig. 30, ax^). It is triangular in shape, connected 

 to the median vein by a membranous fold (g) and to the other axil- 

 laries by membranes only. 



When the radial plate (Hopkins) is not considered as a distinct 

 plate but as a connecting tendon between the second axillary and 

 the radial vein only, the shape and structure of the other axillaries 

 are very much alike in the widely separated genera Dendroctonus Er. 

 and Gnathotrichus Eichh. Further studies will show if this means 

 a parallel modification or if we have to deal with a character common 

 to the superfamily of the Scolytoidea. 



Lateral impression. — An area distinctly impressed on the meta- 

 scutum (fig. 17, q), according to Hopkins, accommodates the flexor 

 plate at rest when the wings are closed. 



