NO. II LARVAE OF THE ELATERID BEETLES GLEN I77 



A. nigropilis Motschulsky : Eight specimens were examined, in- 

 cluding the exuviae of three larvae reared to adults. All were col- 

 lected from the same cottonwood stump. 



8; Lethbridge, Alberta ; June 5, 1935 ; 3 reared adults emerged June 23, July 12, 

 and July 12, respectively; R. Glen. (C.N.C.) 



THE ATHOUS UNDULATUS GROUP 



Figure 36 



KEY TO SPECIES 



Urogomphi (fig. 36, a) with outer prongs slightly shorter than inner prongs; 

 dorsum of ninth abdominal segment with conspicuous pits anteriorly ; 

 mesothorax and metathorax with well-developed impressions on medio- 

 tergites A, undulatus (DeGeer) 



Urogomphi (fig. 36, d) with prongs subequal; dorsum of ninth abdominal 

 segment with conspicuous pits both posteriorly and anteriorly ; meso- 

 thorax and metathorax with very short impressions on mediotergites . . . 

 A. villosus (Geoffroy) 



The larvae of Athous (Harminius) undulatus (DeGeer) and 

 Atlious villosus (Geoffroy) (=A. rhomheus Olivier) are sufficiently 

 closely allied to be placed in the same group until the larvae of other 

 related species are available for examination. Both species occur in 

 Europe and midulatus is reported by Van Dyke (1932, p. 368) also 

 to inhabit the Hudson Bay and Lake Superior regions of North 

 America. The larvae are found in decaying wood and are believed 

 to be predaceous. 



Larvae of this group superficially resemble those of Athous cucul- 

 latus (Say), but differ in characters of the mandible, sculpture of 

 abdominal mediotergites (fig. 36, c), and shape of the caudal notch 

 (fig. 36, a, d). 



Mature larvae usually exceed 20 mm. in length. Dorsum is dark 

 brown to brownish black, with large, deep pits, sometimes confluent in 

 second to sixth segments. Venter pale yellow. Caudal notch at least 

 moderately large, subcircular, much narrowed posteriorly. Urogomphi 

 (fig. 36, a, b, d, e) with subequal prongs, or with inner prongs longer 

 than outer prongs; outer prongs {opr) with bluntly rounded tips. 

 Ninth abdominal segment with large, deep pits on dorsum ; sometimes 

 {villosus) with 2 fine setae anteriorly on dorsal plate; with 3 promi- 

 nent blunt teeth on each lateral margin of dorsum; and distance be- 

 tween caudal notch and pleural area approximating one-eighth of 

 total length of segment, exclusive of urogomphi. Frontoclypeal area 

 truncate (villosus) or broadly rounded (undulatus) posteriorly. Man- 



