172 A YEAR OF COSTA RICAN NATURAL HISTORY 



occupying all of the head; 2, the anterior end of the pro- 

 thorax; 3-1 1, the nine abdominal segments, one pair in 

 each segment, that of the last segment being the largest of 

 the abdominals. 



Pairs I and 2 were much more constantly in activity than 

 the others. The number of the abdominal luminous organs 

 in activity varied from time to time. In some individuals 

 there was only one luminous area on a given abdominal 

 segment, i. e., the right or left organ was absent altogether, 

 functionally at least. Usually when these larvse were 

 crawling over the ground only pairs i and 2 were luminous; 

 when we attempted to pick up the insect the abdominals 

 also became luminous as the larva ran to escape the fingers. 

 The color of the light produced by all the pairs of luminous 

 organs was the same — green. These larvae could run very 

 fast. We could not detect any odor from them nor on the 

 fingers after handling them. The use of this light to the 

 larvae is problematical as in this stage of development it 

 cannot serve as a sexual attraction. Unfortunately, we 

 did not attempt experiments to determine whether the 

 larval light might aid in catching prey. 



Firefiies (Lampyridae) were conspicuous also on these 

 evenings at the beginning of October, usually high, or other- 

 wise inaccessible; we noted their presence here in March 

 also. The light they produced was green. 



In June we had some bright moonlight, the moon being 

 in the second quarter; but several times, between seven 

 and eight o'clock, the mist stole in as a slender finger from 

 the eastern end of the crater, where the railroad entered 

 through a deep cut. Rapidly the mist filled the entire 

 crater, blotting out its edges all around and cutting off the 

 direct moonlight. 



The floor of the old crater, which our cabin faced, was in 

 great part swampy and had been much wetter in earlier 



