FIREFLY GENUS PYRACTONEMA — McDERMOTT 137 



specimens therefore probably represent some local variant of that 

 species, although because of the much reduced pronotal infuscation, 

 they are superficially more like a larger P. latior. 



The almost startling similarity, especially in the pronotal appear- 

 ance, of many of the species has been noted, and applies particularly 

 to the nigripennis group, and also to depressicornis and haemorrhoa. 

 Structurally as well as in coloration, most of the members of the genus 

 are quite similar, which may be taken to indicate relatively recent 

 speciation. The adaptation of P. obscura to the seemingly unfavor- 

 able habitat (from the lampyrid standpoint) of Tierra del Fuego, 

 latitude 55° S., is interesting; Lampyris noctiluca in England and 

 Europe is at about a corresponding latitude north but in a more 

 favorable climate. 



In the course of the work, it was noted that the odor of the collection, 

 especially of the nigripennis group, was very similar to that of collec- 

 tions of the North American Photinus pyralis, though rather more 

 pronounced. Alcoholic extracts of the specimens of this genus did 

 not develop a blue fluorescence as do similar extracts of Photinus. 



While nothing definite is known about the life history of Pyractonema 

 or their habits, the mouth parts are complete, and it may be that the 

 adults feed occasionally, probably on other insects, as is the case in 

 Photuris and Photinus. More probably, most of the feeding is done 

 in the larval stage as is usual among lampyrids, the principal food 

 probably being snails (Pefia). One specimen bore a minute tick. 



The larvae in the collection do not differ materially in superficial 

 appearance from those of North American lampyrids. The largest 

 were 18.35 and 19.65 mm. long by 5.1 and 4.3 mm. broad at the meso- 

 notal and metanotal segments, and taper posteriorly. The pro- 

 notum of the smaller of the larvae was but little narrowed in front 

 and the head was unusually large with very long, slender, tapering 

 mandibles, the distance across the bases of the latter being over 

 1.5 mm. The legs and antennae were also unusually long for a 

 lampyrid larva. It was brown with yellow lateral borders on all the 

 segments, and the abdominal segments have subtriangular laterally 

 projecting plates, all of which present a serrate appearance. The 

 larger larva was practically black, granulose, and had posterolateral 

 angles on all segments which were yellow to a rather bright salmon- 

 pink. The head was much smaller than in the smaller larva, black, 

 cylindrical, and bore a pair of short mandibles slightly curved up- 

 wards. Both larvae had a pair of luminous organs, apparently func- 

 tional, on the lateral thirds of the 8th abdominal segment. I concluded 

 (1956) that the latter one represents a juvenile state of the giant glow 

 worms found in South America. 



