Elmidae, Curtis, 1830

Shepard, William D., Clavier, Simon, Cerdan, Axel & Toulouse, Université, 2020, A generic key to the known larval Elmidae (Insecta: Coleoptera) of French Guiana, Papéis Avulsos de Zoologia 60 (15), pp. 1-9 : 2-3

Key to the larval Elmidae known from French Guiana

1. Pleural sclerites on AB I-VIII; body strongly flattened dorsoventrally; lateral margins of thoracic and abdominal segments with narrow, falcate extensions ( Fig.1 )............................................................................................................................................................................................................. Phanocerus Sharp

1’. Pleural sclerites not as above;body cylindrical,subcylindrical or slightly flattened dorsoventrally;lateral margins of thorax and abdomen without narrow,falcate extension.................................................................................................................................................................................................................................. 2

2. AB IX with pleural sutures extending to middle;body cylindrical ( Fig. 2 ) ........................................................................................................... Cylloepus Erichson

2’. AB IX lacking pleural sutures;body cylindrical,subcylindrical or slightly flattened.......................................................................................................................3

3. AB IX broad,flat,with denticulate lateral margins,tergum with midline row of about six spines (spines may be broken off) ( Fig.3 ).................................Larva V

3’. AB IX not as above ........................................................................................................................................................................................................................ 4

4. Sensory appendage of second antennomere very long, equal or exceeding length of second antennomere; AB IX 2.5× as long as wide; a line of flat, wide tubercles on each side of midline on mesonotum to AB IX; posterior margins of pronotum to AB VIII with row of stout tubercles; AB I-VIII with slightly expanded sides ( Fig.4 )..................................................................................................................................................................... Austrolimnius Carter & Zeck

4’. Not with the above combination of characters ............................................................................................................................................................................. 5

5. Abdominal terga with two pairs of flanges extending above surface ( Fig.5 )..................................................................................................... Neolimnius Hinton

5’. Abdominal terga lacking flanges extending above surface........................................................................................................................................................... 6

6. Procoxal cavities open...................................................................................................................................................................................................................7

6’. Procoxal cavities closed............................................................................................................................................................................................................... 13

7. Mesonotum to AB VIII with dorsal,transverse,broad ridge on posterior border;AB I-VII with posterolateral corners projecting posteriorly;abdominal segments lacking pleurites;AB IX pentagonal in cross section( Fig.6 ) ............................................................................................................................................Larva W

7’. Mesonotum to AB VIII lacking transverse ridge; AB I-VII lacking posterior projections;some abdominal segments with pleurites; AB IX not pentagonal in cross section...................................................................................................................................................................................................................................... 8

8. Only AB I with pleurites ................................................................................................................................................................................................................ 9

8’. AB I-VI or I-VII with pleurites...................................................................................................................................................................................................... 10

9. Lateral sides of AB I-VI extended as quadrate projections;projections laterally denticulate;surfaces not heavily tuberculate;anterior of head lacking blunt,stout setae ( Fig.7 ) ....................................................................................................................................................................................................................Larva Z

9’. Lateral sides of AB I-VI lacking quadrate projections; all surfaces heavily tuberculate; meso- and metasternite with heavily tuberculate triangular projection between coxae;body cylindrical;anterior of head with numerous blunt, stout setae( Figs.8-9 ) .......................................................... Stenhelmoides Grouvelle

10. Pleural sclerites present on AB I-VII ............................................................................................................................................................................................11

10’. Pleural sclerites present on AB I-VI .............................................................................................................................................................................................12

11. Body wide,heavily sclerotized,densely pubescent;AB IX,2.2× as long as wide ( Fig. 10 ) ....................................................................... Potamophilops Grouvelle

11’. Body slender,not heavily sclerotized,not densely pubescent;AB IX,5× as long as wide ( Fig.11 ) .................................................................... Elachistelmis Maier

12. Ventral region of prothorax with four sclerites (one anterior pair and one posterolateral pair); body usually curved in“C”; margin of body lacking many stout spines ( Fig.12 )................................................................................................................................................................................................... Xenelmis Hinton

12’. Ventral region of prothorax with seven sclerites (one anterolateral pair,two lateral pair and one central sclerite);body not“C” shaped;margin of body with many stout spines ( Fig.13 )................................................................................................................................................................................... Stegoelmis Grouvelle

13. Lateral margins of prothorax to AB I overhanging venter of those segments;all surfaces smooth,not tuberculate;body wide anteriorly and tapering posteriorly ( Fig.14 )............................................................................................................................................................................................................... Gyrelmis Hinton

13’. Lateral margins of prothorax to AB I not overhanging those segments;surfaces tuberculate;body not wider anteriorly........................................................... 14

14. AB IX 4× longer than wide .........................................................................................................................................................................................................15

14’. AB IX less than 4× longer than wide .......................................................................................................................................................................................... 16

15. Thorax and abdomen dorsally with tubercles arranged in rows ( Fig. 15 )....................................................................................................... Hexacylloepus Hinton

15’. Thorax and abdomen with tubercles randomly arranged ( Fig.16 ).................................................................................................................... Neoelmis Musgrave

16. Dorsum with tubercles;venter of prothorax with several separate sclerites................................................................................................................................ 17

16’. Dorsum lacking tubercles;venter of prothorax with one large sclerite ( Fig.17 ).......................................................................................................................... 20

17. AB IX with one lateral row of spines on each side ( Fig.17 ).................................................................................................................................... Heterelmis Sharp

17’. AB IX without a lateral row of spines on each side......................................................................................................................................................................18

18. Midline of dorsum with a longitudinal row of yellow spots at intersegmental joints;anterior margin of head lacking large tooth between bases of antennae and clypeus ( Fig.18 )........................................................................................................................................................................................ Microcylloepus Hinton

18’. Midline of body lacking dorsal longitudinal row of yellow spots; anterior margin of head with a large tooth on each side, between bases of antennae and clypeus.................................................................................................................................................................................................................................... 19

19. Body flattened in cross section;mesothorax and metathorax with 2 pleurites;prothorax with distinct suture between coxal cavities and notum ( Fig.19 ).......... ................................................................................................................................................................................................................ Macrelmis Motschulsky

19’. Body semicylindrical in cross section;mesothorax and metathorax with 3 pleurites;prothorax lacking suture between coxal cavity and notum ( Fig.20 )............ ................................................................................................................................................................................................................... Hintonelmis Spangler

20. Prothorax venter with one large sclerite ( Fig.21 ) ................................................................................................................................................................Larva Y

20’. Prothorax with pentagonal prosternum;two pleurites,anterior pleurites meeting at midline,posterior pleurites wrapping around coxal cavities ( Fig.22 )......... .........................................................................................................................................................................................................................................Larva X

Figures

Figures 1-6. Larvalhabitus (dorsal,lateral,ventral).(1) Phanocerus Sharp;(2) Cylloepus Erichson;(3)LarvaV;(4) Austrolimnius Carter& Zeck;(5)Neolimnius Hinton; (6) LarvaW. Scale bars = 1 mm.

Figures 7-13. Larval habitus.(7) Larva Z,dorsal,lateral,ventral;(8) Stenhelmoides Grouvelle,dorsal,lateral,ventral;(9) Stenhelmoides Grouvelle,headand thorax, dorsal;(10) Potamophilops Grouvelle, dorsal, ventral;(11) Elachistelmis Maier,dorsal, lateral;(12) Xenelmis Hinton, dorsal, lateral, ventral; (13) Stegoelmis Hinton, dorsal,lateral,ventral.Scale bars = 1 mm.

Figures 14-19. Larval habitus (dorsal, lateral, ventral). (14) Gyrelmis Hinton; (15) Hexacylloepus Hinton; (16) Neoelmis Musgrave; (17) Heterelmis Sharp; (18) Microcylloepus Hinton;(19) Macrelmis Motschulsky.Scale bars = 1 mm.

Figures 20-22. Larval habitus (dorsal, lateral, ventral). (20) Hintonelmis Spangler;(21) LarvaY;(22)Larva X.Scale bars = 1 mm.