338 



Leech and Chandler: Coleoptera 



are never very long; last glabrous antennal segment — 

 obconic, fitted more or less tightly against 1st segment 

 of pubescent club, which may be loose or compact 

 (fig. 13:32/); 2nd segment of maxillary palpi (1st is 

 very small) much thicker than 3rd or 4th; species 

 terrestial or in damp places. SPHAERIDITNAE 24 15. 



5. Meso- and metasterna with a continuous median longi- 

 tudinal keel which is prolonged posteriorly into a — 

 spine between hind coxae (fig. 13:36a). IIYDRO- 

 PHILINAE 6 



— Meso- and metasterna without a continuous common 16. 

 keel 10 



6. Prosternum sulcate to receive anterior part of meso- 

 sternal keel; metasternal keel projecting beyond hind 

 trochanters as a spine (fig. 13:36a) 7 



— Prosternum carinate, not sulcate; metasternal keel 



not or hardly reaching beyond bases of hind trochanters — 

 9 



7. Larger species, 30 to 45 mm. long 8 



— Smaller species, 6 to 15 mm. long (fig. 13:30c) 



Tropisternus Solier 1 834 17. 



8. Prosternum bifurcate at middle, so that anterior tip 

 of mesosternal keel could contact head 



Dibolocelus Bedel 1892 



— Prosternum sulcate at middle behind to receive meso- — 

 sternal keel, but closed anteriorly, hooded (fig. 13:30a) 



Hyd'/ophilus Geoffroy 1762 



9. Front margin of clypeus simply truncate or arcuate; 18. 

 labrum lacking 2 isolated pores at middle, but with 

 continuous row of setigerous punctures along posterior 

 margin (fig. 13:326); antennal club compact, almost 

 symmetrical Hydrochara Berthold 1827 



— Front margin of clypeus arcuate, and emaxginate at — 

 middle to expose a preclypeus; labrum with 2 small 

 isolated pores at middle, posterior margin with seti- 

 gerous punctures at each side only (fig. 13:32c); 

 antennae perfoliate, of very asymmetric segments 19, 

 N e ohydr ophilus d'Orchymont 1928 



10. First 2 abdominal sternites with a common excavation, 

 large and spectacle-shaped, which is normally filled — 

 with a hyaline transversely bilobed mass, the latter 

 supported by a fringe of long stiff golden hairs arising 

 from anterior margin of 1st sternite; small beetles 20, 



(1-2.5 mm. long) with ability to roll up partly 



CHAETARTHRIINAE . . . . Chaetarthria Stephens 1833 — 



— First 2 abdominal sternites without a broad excavation 21 

 in common; 1st sternite without a fringe of long stiff 

 golden hairs projecting back from anterior margin ... 11 



11. Head markedly deflexed, often with deep transverse 

 groove delimiting a postoccipital region; antennae — 

 usually with only 3 segments before cupule, hence 

 7-segmented; scutellum a long triangle (fig. 13:31a); 

 middle and hind tibiae fringed with long natatory hairs. 22 

 BEROSINAE 12 



— Head not strongly deflexed, without a transverse 

 occipital groove; antennae normally 9-segmented; 

 scutellum not or not much longer than its basal width; 

 middle and hind tibiae without natatory fringes. — 

 HYDROBIINAE 13 



12. Eyes very prominent (protuberant); front tibiae slender 



linear; labrum prominent (fig. 13:31a) 23, 



Serosus Leach 18 17 



— Eyes not prominent; front tibiae triangular, gradually 

 widening from base to apex; labrum very short, not 



prominent; New Jersey to Florida and Alabama — 



Derallus Sharp 1882 



13. Maxillary palpi robust and short, shorter or not much 

 longer than antennae, ultimate segment as long as or 

 longer than penultimate 14 24, 



— Maxillary palpi more slender, longer than antennae, 

 with ultimate segment usually shorter than penultimate 



20 



14. Elytra with sutural striae in at least apical half; — 

 usually only 5 abdominal sternites visible; hind tibiae 



not arcuate; hind trochanters normal, closely applied 

 to femora 15 



Elytra with rows of punctures but no sutural striae; ' 

 5th abdominal sternite truncate or emarginate, usually 

 exposing 6th; hind tibiae arcuate; hind trochanters i 

 large, about 1/3 as long as femora, their apices distinct 



from femora Laccobius Erichson 1837 



Larger species, at least 4.5 mm. long; elytra striate 



or with pronounced rows of punctures 16 



Smaller species, not more than 3 mm. long; elytra 

 impunctate or confusedly punctate, never striate, 



at most with punctures subserially arranged 18 



Segments 2 to 5 of middle and hind tarsi with a fringe 

 of long, fine swimming hairs, which arise from a series 

 of punctures or a narrow groove along upper inner edge 

 of tarsi (hairs often closely stuck along groove in dry 

 or greasy specimens); lateral margins of elytra even 



Hydrobius _ Leach 1815 



Middle and hind tarsi completely without groove and 

 fringe of long swimming hairs along upper inner edge; 

 lateral margins of elytra weakly serrate at least basally 



17 



Form strongly convex, almost hemispherical in profile; 

 clypeus more deeply emarginate, median part nearly 

 truncate; occurs in eastern United States and Canada 



Sperchopsis LeConte 1 862 



Form oval; clypeus evenly, shallowly, arcuately 

 emarginate; occurs in western United States and 



Canada Ametor Semenov 1900 



Prosternum longitudinally carinate at middle; meso- 

 sternum usually with longitudinal median carina behind 

 its anterior transverse A -shaped protuberance; 1st 

 abdominal sternite sometimes with fine longitudinal 



carina at middle P aracymus Thomson 1867 



Prosternum not carinate; mesosternum simple, or with 

 transverse A-shaped or arcuate carina or protuberance, 

 but no median longitudinal carina behind it; 1st ab- 

 dominal sternite never carinate at middle 19 



Mesosternum simple, noncarinate, or with a small 



transverse protuberance before middle coxae 



Crenitis Bedel 1881 



Mesosternum with a prominent angularly elevated or 



dentiform protuberance before middle coxae 



Anacaena Thomson 1859 



All tarsi 5-segmented, though basal segment may be 



very small and difficult to see 21 



Middle and hind tarsi 4-segmented 22 



Curved pseudobasal segment (basal segment is very 

 small) of maxillary palpi with convexity to front; meso- 

 sternum with projecting longitudinal lamina; elytra 



confusedly punctate Enochrus Thomson 1859 



Curved pseudobasal segment of maxillary palpi with 

 convexity to rear; mesosternum at most feebly pro- 

 tuberant Helochares Mulsant 1844 



Anterior coxal cavities closed behind; labrum con- 

 cealed beneath projecting nonemarginate clypeus, 

 which extends around to about middle of each eye, and 

 outward for a distance equal to about width of an 



eye (fig. 13:32a") Helobata Bergroth 1888 



Anterior coxal cavities open behind; labrum fully 

 exposed, clypeus truncate or emarginate, not extend- 

 ing laterally in front of eyes 23 



Maxillary palpi long and slender, pseudobasal segment 

 {- 1st long one) at least 2/3 as long as a front tibia; 

 tarsal claws with broad basal tooth in male, less 

 prominently toothed in female . . .Helocombus Horn 1890 

 Maxillary palpi shorter, stouter, first 2 long segments 

 together subequal in length to a front tibia; tarsal 



claws simple in both sexes 



Cymbiodyta Bedel 1881 



Head not narrowed just in front of eyes, but with 

 expanded margin reaching almost to outer edge of 

 eyes, and hiding bases of antennae (fig. 13:41a). 



SPHAERIDIINI 25 



Head narrowed in front of eyes, outer margin forming 

 an angle with latter; antennal bases visible from 

 above, not concealed under margin of head (fig. 13:416) 

 27 



