THE CANADIAN ENTOMOLOGIST. 1 77 



light organs are varied, sometimes brilliant in both sexes, sometimes weak 

 in both sexes, and sometimes brilliant only in the £ . Their food consists 

 of small terrestrial mollusca. 



The third category, B, consists of Phengodes and allied genera in 

 which the side pieces of the metathorax are wide. I know nothing by 

 observation of the luminous qualities of these insects, of which only 

 males are known. They are all rare, and I have seen none alive. But 

 we here owe our special thanks to Mrs. King for the patient quest which 

 has been rewarded by the discovery of the pupa of Phengodes, and which 

 will probably result in another season in the detection of the larva. * 



I am also indebted to Mrs. King for a larva of Mastinocerns, of 

 slender, cylindrical form and pale color. It was feebly luminous, and 

 lived upon small snails. The perfect insect is thus mentioned in a letter, 

 the observations being made upon a specimen attracted by the lamp : 

 " June 4th saw running rapidly over the table near a lighted lamp, a small 

 Coleopter ; it was twisting its abdomen up over its wings, and evidently 

 trying to straighten them out, as they seemed moist and twisted at their 

 ends. The general appearance suggested Mastinocerus, and acting on 

 this thought, I captured it and sat up till a late hour to be assured of the 

 truth. The insect was in a small vial, and moved quickly. It gave out 

 light conspicuously from the head, feebly from the anal end, and still more 

 so from about the base of the abdomen. The light seen in the head, 

 though visible in the dark as a round spot, yet when taken into a room 

 obscurely lighted was invisible from above ; but when the insect was sud- 

 denly thrown upon its back a light no larger than a pin point was seen 

 just about the junction of the head and prothorax." . . 



It is quite possible that the genera of the other continent constituting 

 the sub-family Drilidae should be placed as a group of this series ; but 

 upon this point I cannot speak with confidence, as I have had no oppor- 

 tunity of studying them carefully. They live on snails, and some of them 

 pass through their transformations in the shells of the animals upon which 

 they have fed. 



* It is still uncertain whether the large luminous larvae described by Baron Osten 

 Sacken (Proc. Ent. Soc. Phila., i., 125, pi. 1, f. 8) belong to the Elateride Melanactes 

 or to Phengodes. Species of both genera are found in nearly all parts of the United 

 States, but though the larvae seem to resemble that of Mastinocerus referred to in the 

 text more than any described Elateride larva;, it is more probable that they should be 

 referred to the latter family. 



