514 FAUNA HAWAIIENSIS 



middle of the base of the pronotum is very often differently sculptured to the rest ; 

 slightly impressed and bounded in front by a transverse slightly arcuate line. But no 

 species except A. iiisu/aris has the laasal chain of strong, very clear-cut punctures. The 

 characters chiefly used in distinguishing species are, form and proportions of presternum, 

 form of mesosternum, presence or absence of the special sculpture at the base of the 

 pronotum, and general sculpture and punctuation. 



In all species the dorsal surface of the neck has a fine transverse, slightly reticulate 

 striation (shown only in PL XV. figs. 3, 18), which may act against the front of the 

 pronotum as a stridulating organ. 



An attempt to tabulate all the species has proved unsuccessful ; only the following 

 divisions can be made ; — 



Section I. .Scutellum visible, distinct no. i . 



Section II. Scutellum invisible. 



II A. Diverging striae on metasternum and first abdominal segment curved 

 up behind co.xae nos. 2 — 33. 



II B. Diverging striae ending blindly, not curved up behind coxae ...no. 34. 



The 32 species of division II A can only be placed in the following rough groups, 

 which it is hoped may possibly be of some assistance : — 



Group 1. Forms at least 1^ mm. long, very distinctly punctured (or rugose, in 

 A. oi-natus, no. 2), with no impressed area at base of thorax, first abdominal segment 

 as strongly punctured as metasternum. Metasternum not impressed nos. 2 — 9. 



Group 2, Strongly sculptured forms, with larger punctures (but no impressed 

 area) at the base of the thorax ; with metasternum strongly punctured but first abdo- 

 minal segment almost impunctate. Mesosternum with no definite impression 



nos. 10 and 1 1. 



Group 3. Depressed, with punctures more or less aciculate, with impressed area 

 at base of thorax bounded in front by a transverse line [except in no. 12, A. luaianaae, 

 where it is absent or indefinite]. Mesosternum impressed nos. 12 — 17. 



Group 4. Forms in which the elytra are punctured only over a small area near 

 the suture ; with impressed area at base of thorax ; mesosternum impressed 



nos. 18 and 19. 



Group 5. With distinct, sometimes aciculate punctures. Keel of prosternum long 

 and narrow, 2 J to 3 times as long as broad. Mesosternum impressed. [No. 21, 

 A. monticola, has no impressed area at base of thorax. No. 20, A. siinih's, has a slight 

 one, and is in many ways related to Groups 3 and 4] nos. 20 and 21. 



