1910.] 179 



TABLE OF THE BEITISH SPECIES OF PTENIDIUM, Er. 



1 (18). Sciitellary furrow with a miniite but distinct middle keel. 



2 (7). Prosternal keel broad and fui-rowed in nearly its entire length... 



Sub-genus Matthewsium, Flach. 



3 (4). Thorax broadest at the base, the two middle basal fovese wanting. 



Body regularly egg-shaped ; upper-side castaneous-brown ; pube- 

 scence scanty, extremely short and scarcely visible ; elytra some- 

 times paler at base, very finely ahitaceous ; sciitellvun with 

 punctures in basal furrow absent or obsolete... 



Length, 0.8 — 0.84 mm. P. gress7ieri, Gillm. 



4 (3). Thorax broadest a little before base, basal fovese small but distinct, 



middle pair placed at some distance from base ; scutellum with 

 a very minute (and in turgidum sometimes obsolete) punctvire, 

 placed between the middle keel and side-angles, but rather nearer 

 to the latter. 



5 (6) Upper-side distinctly akitaceous, with fine, scattered, shallow punctures 



and scarcely v isible pubescence ; thorax not strongly margined ; 

 scutellum witli a distinct puncture on each side of middle keel, 

 placed as above; elytra usually castaneous-brown, the head and 

 thorax darker, but coloiar somewhat variable... 



Length, 0.86 — 0.94 mm. P. Isevigatum, Gillm. ^ 



6 (5). Upper side with distinct hairs, which are especially long on sides of 



thorax ; tliorax strongly margined, with punctuation rather strong 

 and deep ; scutellum with punctures extremely small or obsolete ; 

 elytra not or scarcely alutaceous ; body broader in proportion to 

 its length than that of Isevigatum... 



Length, 0.92 mm. P. turgidum, Thoms. 



7 (2). Prosternal keel simple, at least in front; thorax broadest a little 



before base. 



8 (9). Scutellum with about six minute semi-equal ridges on each side of 



central keel, the interspaces being punctiform," without larger 

 puncture close to the side angles ; prosternal keel with a short 

 furrow between the anterior coxae... 



Sub-genus Wankow^izium, Flach. 



Basal thoracic fovese very small ; thorax and elytra with widely and 

 irregularly placed shallow punctures ; elytra usually castaneoiis, 

 with somewhat raised scattered hairs, fore-parts darker... 



Length, 0.86 — 0.92 mm. P. intermedium, Wank.^ 



1 P. hruckii, Matth. (Trichopt., 82), WoU. (Cat. Col. Canar., 104), can hardly be said to have 

 even varietal differences from Icevigatum, Gillm. The fact that Matthews confused the latter 

 species with m>/rmecophilum, Mots., and that the Uevtgatutn of his collection are nitiJum, Heer, 

 wiU account for this and some other of his mistakes. The types of P. hruckii are from the Canary 

 Islands (Crotch). Other specimens under this name are labelled " Morocco," "Italy," &c. 



2 Wankowiez says "crenate," Flach describes them as "tj punctures"; either is correct- 

 Somewhat similar ridges are often found in P. fuscicorne, but they are less regular, being 

 strongest near central ridge, and becoming progressively weaker as they approach the large 

 jiuncturc in side-angles. P. Juscicorne may also bo distinguished by its black colour and much 

 loiiger pubescence. 



3 The name " inlerniediuin, Wank.," must be retained, Gyllenhal's " intermedium " is a 

 2'richopteryx. Matthews's type of wankowiezii is a rubbed specimen of pusillaw, GyU. 



