313 

 Leech and Chandler: Coleoptera 



10. 



11. 



12. 



13. 



Frontal projection with a notch at each side (fig. 13:10;') 



3 



Frontal projection without notches 4 



Cerci with only primary hairs, 6-7 in number (fig. 



13:10n) Hydroporus Clairville 1806 and 



Hygrotus Stephens 1828 



Cerci with additional secondary hairs (fig. 13:10Z) 



Oreodytes Seidlitz 1886 (in part), 



and Deronectea Sharp 1882 



Larva not greatly widened; last abdominal segment 

 long and tapering; cerci with only primary hairs .... 



Bidessus Sharp 1 882 



Larva greatly widened in middle; last abdominal seg- 

 ment long or short; cerci long with secondary hairs, 



oi* short with primary hairs only 5 



Last abdominal segment long and tapering; cerci 

 short, arising beneath segment, projecting beyond it, 

 and having primary hairs only (fig. 13:11a) 



Hydrovatua Motschulsky 1855 



Last abdominal segment short; cerci long, with second- 

 ary hairs. Oreodytes Seidlitz 1886 (in part) 



Maxillary stipes broad, suboval, usually with 1 to 2 



strong inner marginal hooks (fig. 13: lid) 7 



Maxillary stipes very long and slender, with no inner 



marginal hooks (fig. 13: 1 lc) 18 



Abdominal segments 7 and/or 8 laterally without 



fringe of long swimming hairs; ligula absent 8 



Segments 7-8 with swimming hairs; ligula present . . 14 

 Fourth (last) segment of antennae less than 2/3 the 



length of 3rd 9 



Fourth segment more than 2/3 the length of 3rd 



. .Rhantus Dejean 1833 and Colymbetes Clairville 1806 

 Mandibles toothed along inner edge, 4th antennal 

 segment double (biramous) (fig. 13: 11 6) 



Copelatus Erichson 1832 



Mandibles not toothed, 4th antennal segment not double 



Cerci with numerous secondary hairs (fig. 13:11/:); 

 4th antennal segment less than 1/4 as long as 3rd; 

 front constricted just below acute apex, head gradually 

 narrowed posteriorly without occipital suture or shallow 

 groove defining neck area, anterior abdominal spiracles 

 in the membranous area (fig. 13:11/) 



Laccophilus Leach 1817 



Cerci usually with 7 primary bairs in 2 whorls, 3 near 

 middle, 4 apically (fig. 13:1 1 Z)» 4th antennal segment 

 about 1/2 as long as 3rd, apex of front obtuse, anterior 

 abdominal spiracles on the margin of the tergites ... 11 

 Thorax as wide as long, about equal in length to 

 abdomen, sides of head nearly round without neck 

 area set off by shallow groove 



Hydrotrupes Sharp 1882 



Thorax longer than wide, never as long as abdomen, 

 sides of head round or squarish but with neck area 

 set off by occipital suture or shallow groove (fig. 



13:1 1^) 12 



Tibia and tarsus with conspicuous spines confined to 

 apical half, mostly terminal; dorsal margin of middle 

 and hind femora without row of spines; tergites, from 

 2nd thoracic to 8th abdominal, bearing 3 or more pairs 

 of long conspicuous setae, venter of abdominal seg- 

 ments 4 to 6 with a similar pair of setae 



Agabinus Crotch 1873 



Tibia and tarsus with spines not confined to apical 

 half; dorsal margin of middle and hind femora with 

 row of spines; anterior tergites and sternites (see 

 above) usually without conspicuous setae, or if present 

 they are much smaller than those on 8th and 9th 



segments 13 



Lateral margin of head more or less compressed or 

 keeled, with temporal spines on a line which would 

 intersect the ocelli or pass just below them (fig. 13 : 1 1 i) 



Ilybius Erichson 1832 



Lateral margin of head not keeled, temporal spines 

 on a line which would run well below the eye (figs. 

 13:11;', 13:12a) Agabus Leach 1817 



Fig. 13:12. Dytiscidae. a, Agabus tristis, larva; b, Acnius 

 sulcatus, head of larva to show bifid ligulo; c, Hydaticus sp., 

 abdominal tip and cerci of larva; d, Dytiscus sp., abdominal tip 

 and cerci of larva; e, Hygrotus impressopunctatus, female form 

 lir. .ellus, dorsal view of adult (a, Kincaid, 1900; b, Fiori, 1949; 

 c,d, Wesenberg-Lund, 1912; e, Gellermann, 1928). 



14. With a pair of long, lateral gills on the 6 anterior 

 abdominal segments (fig. 13:66) COPTOTOMINI ... 



Coptotom.ua Say 1834 



— Lacking gills on abdominal segments. THERMONEC- 

 TINAE 15 



15. Ligula very short, armed with 4 spines. ERETINI 

 Ere tea Laporte 1833 



— Ligula long, simple or bifid but without 4 spines 

 (fig. 13:lle). THERMONECTINI 16 



16. Ligula apically bifid (figs. 13:126, 13:14a) 



Aciliua Leach 1 81 7 



— Ligula simple 17 



17. Ligula not as long as 1st segment of labial palp 

 Thermonectua Dejean 1833 



— Ligula nearly equal to or exceeding length of 1st labial 

 palpal segment Graphoderua Sturm 1834 



18. Head anteriorly dentate (fig. 13:13d); ligula long; 

 cerci absent. CYBISTRINI 



Cybiater Curtis 1827 



— Head anteriorly lacking dentation; ligula absent, or 

 low and bilobed; cerci present. DYTISCINI 19 



