March, I9I7-] WiLLIAMS : NORTH AMERICAN LaMPYRID/E. 31 



served an adult female bred in the laboratory, and probably a day old, 

 which on being brought into darkness, was found to have the adult 

 as well as the larval light-organs shining steadily, and in addition, the 

 vertex and frons of the head (where the chitin was transparent) 

 shone also. The dorsum of the thorax down to the abdomen, in the 

 more transparent portions, had an unmistakable glow. Such condi- 

 tions however were not found in the field, nor upon dissecting older 

 specimens. It is evident that a considerable time must elapse after 

 it has hatched from the pupa before the insect is really firm and ma- 

 ture, when the photogenic granules are seen to glow only in the lumi- 

 nous organs of the adult. 



But little was done on the internal anatomy of this insect. The 

 larval digestive and nervous systems are practically the same as in 

 Lampyris noctiluca, as figured by Vogel (1915). If we compare the 

 nervous system of the larva and adult Photiiris, the following points 

 will be noted: the larva has a total of thirteen distinct ganglia in the 

 nervous system, the adult twelve; in the former the brain is in the 

 cervical region, behind the head, and the last two abdominal ganglia, 

 the seventh and eighth, the latter being compound, are separated by a 

 distinct though comparatively short pair of connectives; in the adult 

 the brain, of course, lies within the head and is more closely connected 

 with the subcesophageal ganglion, the first abdominal is very near to, 

 though distinct from the third thoracic ganglion and the seventh and 

 eighth are fused into one oblong ganglion with a median constric- 

 tion. Thus it is seen that there is no considerable difference between 

 these generalized systems in the larva and adult. 



Resume. 



1. Biological studies were made on six different species of fireflies 

 in New England, viz., Photinus consanguineus, and scintillans, Ellych- 

 nia corrusca, Lucidota atra, Pyratomena sp. and Photuris pennsyl- 

 vanica. 



2. Of these, Photuris pennsylvanica is the most brilliant and El- 

 lychnia corrusca the faintest in luminescence in the adult stage. 



3. In the case of Photuris and Photinus at least, the larval light 

 organ is different from that of the adult one which replaces it at 

 maturity. 



4. The light organ of the adult is probably used chiefly for the 



