NO. II LARVAE OF THE ELATERID BEETLES GLEN 39 



narrow. *Antennae with basal segment longest and terminal seg- 

 ment shortest. One to 6 "sensory" appendices on second segment of 

 antenna. * Mandibles with well-developed retinaculum and without 

 other prominent teeth. Proxistipes and dististipes not distinct except 

 in rotundicolUs group. From 2 to 8 prominent setae on antero-latero- 

 ventral aspect of stipes. *Second segment of maxillary palpi without 

 setae. Postmentum with i or 2 setae at each corner. * Second seg- 

 ment of labial palpi not longer than first segment. Presternum of 

 prothorax of 1,2, 3, or 4 sclerites. Each episternum of mesothorax 

 and metathorax without spinelike setae or bearing from i to 10 such 

 setae. Legs bearing many spinelike setae, number and arrangement 

 variable. '''Abdominal mediotergites (segments i to 8 inclusive) usu- 

 ally punctulate without prominent transverse rugae or large deep 

 pits. Abdominal mediotergites bearing "impressions," length vari- 

 able ; setal pattern highly variable in both number and arrangement. 

 Abdominal pleurites vary from "almost wanting" to well developed. 

 Sternum in first to eighth abdominal segments either of i or 3 sclerites. 

 Abdominal spiracles usually subequal and in anterior half of each 

 seginent; sometimes in posterior part of eighth segment; sometimes 

 enlarged in eighth segment. Tenth abdominal segment with anal 

 aperture linear or T-shaped. 



KEY TO "species GROUPS" AND ISOLATED SPECIES OF LUDIUS ^ 



1. Caudal notch large (figs. 13, h, i; 14, c, i) 2 



Caudal notch small (figs. 11, f, h; 14, b, g) 12 



2. Presternum of prothorax divided into 2 or more sclerites (prst, figs. 



10, d; 13, a) ; eyes present (indistinct in edwardsi and semi- 



vittatus groups ) 3 



Presternum of prothorax undivided, of i large triangular sclerite {prst, 

 fig- I3> b) ; eyes absent; ninth abdominal segment (fig. 12, e) 



as figured divaricatus (LeConte) (p. 118) 



3.S Urogomphi u'ith tips of outer prongs sharp and inclined backward 

 {opr, fig. 13, d, c, f, i) ; spinelike setae present on episterna of 

 mesothorax and metathorax ; abdominal mediotergites with promi- 

 nent posterior setae arranged in pairs (fig. 14, e, f) (species pri- 

 marily phytophagous) 4 



5 This key does not include the European species Ludius melancholiciis (Fab- 

 ricius), L. amplicollis (Germar), and L. ajfinis (Paykull). Larvae of these 

 species were not available for examination and key characters and relationships 

 are not known. For descriptions of these species see pp. 64, 64, 93, respectively. 



^ In this couplet, any one of the three characters listed will provide proper 

 separation of the larvae. The urogomphal prongs are most readily observed, 

 but this character must be used with care because the tips of the prongs are 

 sometimes worn off. 



