THE STINK-BUGS. 



93 



very rapid motion, evidently for the purpose of protecting the 

 young from the apprehended danger." -"• 



Exclusive of the subfamily Graphosomatinae, Van Duzee in 

 his Catalogue lists from America north of Mexico 159 species 

 of Pentatomidae, distributed among 50 genera. Of these 97 

 species, representing three subfamilies and 42 genera, are 

 known to occur in the territory covered by this work. The prin- 

 cipal literature treating of our North American species is as 

 follows: Stal, 1867, 1870; Van Duzee, 1904, 1909; Schouteden, 

 1905, 1907; Bergroth, 1907, 1914a; Summers, 1898; Zimmer, 

 1911; Parshley, 1915; Hart, 1919; Stoner, 1920. 



Fig. 18. Ventral and dorsal views of heads of Pentatomid;e. a and d, of Rhy- 

 tidolomia; b, of Apateticus; c, of Brochymena. (After Parshley in Psyche). 



KEY TO SUBFAMILIES OF PEXTATOMID^E. 



«. Tarsi 3-jointed; sternum of thorax (except in Edessa and Arvelius) 

 without a central ridge or keel. 

 b. First segment of beak slender, embedded between the bucculae, 

 which are wide and parallel (fig. 18, a) ; base of beak distinctly 

 separated from end of tylus. Subfamily I. Pentatomin^e, p. 93. 

 bb. First segment of beak short and thick, free, only its base being be- 

 tween the bucculae, which converge and unite behind or beneath 

 the beak (fig. 18, b) ; base of beak close to end of tylus. 



Subfamily II. Asopin^:, p. 178. 



(ia. Tarsi 2-jointed; sternum of thorax with a lengthwise central ridge 

 or keel ; f rena very long, almost reaching tip of scutellum. 



Subfamily III. Acanthosomin^e, p. 204. 



Subfamily I. PENTATOMIN^E Stal, 1864, 32, 76. 



This subfamily contains the large majority of our stink-bugs. 

 They vary much in size and appearance, but agree in having 

 the body more or less oval and subdepressed ; head porrect or 

 nearly so ; bucculae parallel, not united behind, forming a groove 

 for the reception of the basal joint of the beak which is normal 



25 Kirby & Spence. Introduction to Entomology. 6th Ed.. 1859, 203. 



