158 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. Ill 



distinct from all other known larvae in this complex of related genera. 

 Group II is separated from Elathous bicolor and Ludius resplendens 

 through the absence of the mediodorsal groove on the ninth abdominal 

 segment, and from larvae of the Ludius Imioniiformis group by the 

 blunt "teeth" on the same segment. 



Linionius larvae may be characterized as follows: Dorsum pale 

 yellow (or orange-yellow) to yellow-brown, with minute (incon- 

 spicuous) to moderate-sized punctures, but lacking prominent trans- 

 verse rugae. Caudal notch small. Urogomphi bifid, prongs subequal 

 or outer prongs shorter than inner prongs. Ninth abdominal seg- 

 ment usually without a mediodorsal groove, and without "teeth" or 

 with well-rounded "teeth" on lateral margins of dorsum. Nasale vari- 

 able, but usually tridentate at tip. Frontoclypeal area truncate or 

 broadly rounded posteriorly. Eyes present or absent, with 2 to 4 

 setae around eye region. Usually 2 unpaired lateroepicranial setae on 

 each gena. Gula short and narrow. One "sensory" appendix on 

 second segment of antenna. Mandibles variable (figs. 30, c, e; 32, h). 

 Presternum of prothorax (fig. 31, c) undivided. Mesothorax and 

 metathorax with impressions on mediotergites. Abdominal medio- 

 tergites with impressions of varying length ; and usually with 5 to 7 

 prominent setae in posterior transverse row, definitely arranged as 

 2 or 3 pairs in nearly all species. 



KEY TO "species GROUPS" AND ISOLATED SPECIES OF LIMONIUS 



1. Outer prongs of urogomphi reduced to the size of small tubercles {opr, 



figs. 2,o,d,f;2,i,d,e) 2 



Outer prongs of urogomphi pronglike {opr, figs. 30, h; 31, /; 32, d, ^) . . 5 



2. Ninth abdominal segment with 2 conspicuous conical protuberances {pro, 



fig- 31. c, g) pectoralis LeConte (p. 161 ) 



Ninth abdominal segment without such protuberances 3 



3. Mandible (fig. 30, c) with prominent toothlike expansions anterior to 



retinaculum; nasale {n, fig. 30, a,b) short, with 3 subequal teeth 



the aeneoniger group (p. 159) 



Mandible without toothlike expansions anterior to retinaculum 4 



4. Eyes absent ; ninth abdominal segment without a definite mediodorsal 



groove; each paranasal lobe with a cluster of 12 or more "sensory" 



pores {pulp, fig. 2^, a) aeger LeConte (p. 163) 



Eyes present ; ninth abdominal segment with a mediodorsal groove ; para- 

 nasal lobes without definite cluster of pores 



unidentified, possibly confusus LeConte (p. 162) 



5. Nasale {n, fig. 30, g) of i pointed tooth; mandible (fig. 30, e) with very 



large retinaculum and expanded medioventral cutting edge; 



European pilosus (Leske) (?) (p. 160) 



Nasale {n, figs. 31, b; 32, a) with tip tridentate; mandible (fig. 2'^, b) 

 without above characteristics ; North American, .the canus group (p. 164) 



