360 



Leech and Chandler: Coleoptera 



10 



11 



12. 



15 



16, 



17. 



Last abdominnl segment never more than 4 times as 



long as wide 5 



Head with short erect spines, body more cylindrical, 



color yellowish (fig. 13:50c) Narpus Casey 1893 



Head without erect spines, body more hemicylindrical, 



color dusky Rhizelmis Chandler 1954 



Procoxal cavities open behind (fig. 13 :5 lp) 7 



Procoxal cavities closed behind by a definite sclerite 



or sclerites lf> 



Protopleura divided into 3 parts (fig. 13:5 1#) 8 



Protopleura divided into 2 parts 13 



Body hemicylindrical in cross section (fig. 13:50a) . 



Zaitzevia Champion 1923 



Body subtriangular in cross section 9 



Dorsum of body with a medial and lateral pair of 

 prominences or humps on each bodv segment (fig. 



13:50c/) 10 



Dorsum without humps 11 



Body segments without lateral prominences; meso- and 

 metapleura divided into 2 parts; 2 longitudinal dark 

 marks on each thoracic tergite; southeastern U.S. 



Gonielmis Sanderson 1954 



Body segments with lateral prominences (fig. 13:50c/); 

 meso- and metapleura in 1 piece; no dark marks on 



thoracic tergites; eastern U.S 



Promoresia Sanderson 1954 



Meso- and metapleura 1 piece (fig. 13:51/) 



Optioservus Sanderson 1954 



Meso- and metapleura divided into 2 parts 12 



Tubercles on dorsum separated by less than their 

 own widths, uniform in distribution except along 

 posterior margin of segments where they are nearly 

 touching, with broad, flat spines less than length 

 of tubercles; anterior mesopleurae about 1/2 the size 



of posterior Heterlimnius Hinton 1935 



Tubercles sparse, separated by more than their own 

 widths except double row along medial line, large 

 smooth areas on pronotum, and 9th abdominal segment; 

 marginal tubercles separated by their own widths, 

 spines longer than tubercles; anterior mesopleural 



sclerite equal to posterior 



Limnius Erichson 1847 



Abdomen with pleura on segments 1 to 7 14 



Abdomen with pleura on segments 1 to 6 15 



Dorsum of body with dense medial and lateral patches 

 of spatulate spines, making the body appear sub- 

 triangular in cross section 



\mpumixis Sanderson 1954 



Dorsum of body evenly rounded from side to side, 

 hemicylindrical in cross section, with spatulate spines 



limited to the posterior fringe of each segment 



Cleptelmis Sanderson 1954 



Form more slender and cylindrical, abdominal seg- 

 ments twice as wide as long, 9th abdominal segment 

 with convex sides, tip roundly and shallowly emarginate 

 dorsally without spines .... Cleptelmis Sanderson 1954 

 Form more robust and hemicylindrical, abdominal 

 segments 3 times as wide as long, 9th abdominal 

 segment with conical sides, tip deeply emarginate 



dorsally, so as to form 2 lateral spines 



Macronychus Muller 1806 



Lateral margins of abdominal segments 1 to 8 produced 

 posteriorly into spinelike processes (fig. 13:52c/); 



body form wider and less convex 



Ancyronyx Erichson 1847 



Lateral margins of segments not produced, body shape 



hemicylindrical to cylindrical 17 



Protopleura extending to medial line both anterior 

 and posterior to coxal cavities, sternum surrounded 

 and reduced to a triangular sclerite between posterior 

 Yz of coxal cavities, meso- and metapleura undivided, 

 with only sternopleural suture present (fig. 13:51a) 



Cylloepus Erichson 1847 



Prosternum separating the pleura posteriorly, meso- and 



metapleura divided into 2 or 3 parts 18 



Meso- and metapleura divided into 3 parts 19 



— Meso- and metapleura divided into 2 parts (fig. 13 :5 1A> 



20 



19. Dorsal half of all segments except prothorax and 9th 

 abdominal segment with tubercles bearing erect spatu- 

 late spines, arranged in 10 prominent longitudinal 

 rows; 9th abdominal segment strongly triangular with 

 a medial and lateral rows of tubercles (figs. 13:50e, 

 13:5 lb) Heterelmis Sharp 1882 



— Only the medial part of the dorsal half of the body show- 

 ing any tendency for tubercles to be arranged in rows 

 (fig. 13:52/); tubercles without erect spatulate spines; 

 9th abdominal segment rounded (last instar of) .... 



Microcylloepus Hinton 1935 



20. Procoxal cavities not closely approaching lateral 

 margin, separated from each other by a small, un- 

 attached sclerite or by the projection of the sternum 

 forward to unite with pleura 21 



— Procoxal cavities narrowly separated from lateral 

 margin, separated from each other by propleural inter- 

 coxal process projecting posteriorly under the sternal 

 intercoxal process (fig. 13:52e) 23 



21. Procoxae separated by a small, elongate, unattached 

 sclerite lying between procoxal cavities, not covered 

 by pleura anteriorly or sternum posteriorly (fig. 13:51c/); 

 (first instars of) Microcylloepus Hinton 1935 



— Procoxal cavities usually separated by the extension 

 of the sternum forward to meet the pleura; if sclerite 

 between coxae is present it is reduced in size and 

 partly covered by the sternum 22 



22. Anterior margin of head on each side with a large, 

 conspicuous tooth (fig. 13:51c) 



.' Elsianus Sharp 1882 



— Anterior margin of head without a distinct tooth on 

 each side Neoelmis Musgrave 1935 



23. Propleura divided into 2 parts by a short suture from 

 coxal cavity to margin, also with a medial suture 

 in front of coxae; 1st antennal segment more than 

 1/2 as long as 2nd Stenelmis Dufour 1 835 



— Propleura with above sutures obliterated, only sternal 

 pleural sutures faintly visible; 1st antennal segment 

 less than 1/2 as long as 2nd 



Ordobrevia Sanderson 1953 



Key to Nearctic Genera of Elmidae 

 Adults 



1. Adults terrestrial, rarely entering the water; body 

 with pubescence but without tomentum; procoxae trans- 

 verse, trochantin exposed. LARINI 2 



— Adults aquatic; body beneath with tomentum; front 

 coxae rounded, trochantin concealed. ELMINI 3 



2. Antennae clubbed; pronotum with basal sublateral 

 sulcus connecting with margin at middle; elytra with- 

 out accessory striae Phanocerus Sharp 1882 



Fig. 13:55. Elmidae, adults, o, Neoe/m/s /ongu/a; b, 

 Hexacylloepus apicalis (Hinton, 1940). 



