NO. II LARVAE OF THE ELATERID BEETLES GLEN 183 



Genus CRYPTOHYPNUS Eschscholtz 

 Figures 10, g; 38 



The name Cryptohypnus has been used in the present study for 

 species which, on the basis of larval characters, obviously are allied 

 to Cryptohypnus riparius (Fabricius) (=Hypnoidus riparius), and 

 for which American authors recently have shown a preference for 

 the generic name Hypolithus Eschscholtz. The name Hypnoidus 

 Stephens is restricted to species whose larval characters stamp them 

 as being congeneric with H. dubius (Horn) and generically distinct 

 from riparius and its close allies. 



Characters given for this genus are based upon a study of the 

 larvae of the five species listed in the key. All are believed to be 

 soil inhabiting, and some are important crop pests. 



These larvae superficially resemble Melanactes densus and the 

 Ludius nitidulus group but are much more closely allied to the genus 

 Crepidomenus. Cryptohypnus larvae are distinguished by a combina- 

 tion of characters involving setal arrangement, sculpture, and features 

 of the ninth abdominal segment, the following being of primary sig- 

 nificance: Head bearing dorsal posteroepicranial setae {ped, figs. 

 ID, g; 38, a) ; each thoracic segment and first 8 abdominal segments 

 bearing medial anterotergal setae {atm, figs. lo, g; 38, /) ; abdominal 

 mediotergites with impressions and setal pattern as in figure 38, /, 

 setae numbered i to 9 being present in all species ; dorsum of ninth 

 abdominal segment (fig. 38, i) bearing 4 setae on central plate and 

 blunt "teeth" {to) on the margins. 



The species studied rarely exceed 16 mm. in length. Dorsum yel- 

 low to yellowish brown; finely punctulate. Caudal notch {en) large. 

 Urogomphi bifid, prongs subequal in length (fig. 38, e, g) or inner 

 prongs longer (fig. 38, h, i) . Ninth abdominal segment without median 

 dorsal groove, and distance between pleural area and caudal notch 

 varies from one-sixth to one-fourth length of segment, exclusive of 

 urogomphi. Nasale {n, fig. 38, b-d) typically tridentate; lateral 

 denticles may be serrate (fig. 38, d) or absent through erosion. Eyes 

 present. Gula moderately narrow. One "sensory" appendix on second 

 segment of antenna. Mandibles of same type as in Ludius aeripennis. 

 Presternum of prothorax of more than i piece, the median posterior 

 sclerite being very narrow and often indistinct. Mesothorax and 

 metathorax with distinct impressions on mediotergites; and with 

 I to 3 setae on each episternum, setae usually fine or with only i being 

 spinelike. Abdominal pleurites well developed, decreasing in size from 

 first to eighth segments. 



