22 Rev. H. S. Gorham's materials for a 



Photinus, Castelnau, Ann. Fr. p. 141. 

 Type, P. coruscus, Linn. 



This genus is the one of which the study is attended 

 with most difficulty among the LampyridcB. The cha- 

 I'acters laid down by Castelnau are too general, and 

 include the genera Cratomorphus, Lucernula, Aspido- 

 soma and Photuris. No account is taken of the sexual 

 characters to be found in the terminal plates of the 

 abdomen. Motschulsky's numerous subdivisions are un- 

 tenable, being based chiefly on the number of light-giving 

 segments, or rather on those apparently so, for it is not 

 known that this effect is confined to the white or yellow 

 portions of the abdomen. Lacordaire has left little to be 

 desired in his exhaustive resume of characters, and he 

 has described the sexual distinctions [Genera des Col. 

 iv. p. 306], but he appears to have considered them not 

 to have generic value. I have, however, found them to 

 be very constant and useful in this respect. The three 

 last segments beneath and the pygidial above are fi'e- 

 quently emarginate, sinuate or triangularly notched. The 

 males are in general much commoner in collections than 

 the females. They have eight ventral plates, the seventh 

 generally very short. The females have the seventh or 

 apical ventral plate nearly as wide at its base as the pre- 

 ceding one, and triangularly narrowed to the apex, which 

 is always cut out in a notch in this genus. In one species, 

 at least, longipennis, Mots., the abdomen is much enlarged 

 and the elytra are shortened in the female. M. Lacordaire 

 cites lonf/ipennis, Mots., as the type, but it is inconvenient 

 to take that species, for Castelnau did not give it under any 

 name, and it was not described till 1853. I have taken 

 coruscus, L., as being the earliest species described. 



I have found it convenient to retain Pyrectomena, Lee, 

 as a distinct genus. The species forming this group have 

 a very pecidiar and uniform facies, the abdominal plates 

 are also sufficiently different from true Photinus. (See 

 Plate, fig. 14.)* 



I now briefly recite those species which, up to the 

 present time, I have been able to identify; my knowledge 

 of the described species is not sufficient to justify me in 

 describing many of the South American species. I have, 

 however, given the characters of the very interesting- 

 collection lately arrived fi-om Guatemala. 



* The Plate to illustrate the abdominal segments will appear in the 

 next Part. 



