242 A YEAR OF COSTA RICAN NATURAL HISTORY 



that the excrement for the growth of the fungus may well 

 be furnished by the caterpillar or by some of the beetles 

 which were found there. This affords, then, a glimpse of 

 the food dependence of a member of the second group on 

 those of Seiior Picado's first group. 



The predaceous members, like their non-bromelia-dwell- 

 ing relatives, do not hesitate at cannibalism. The alimen- 

 tary canal of a larva of Mecistogaster modestus taken on 

 April 26 contained a smaller larva of the same species, a 

 mosquito larva and a copepod crustacean. Larvae of 

 mosquitoes of the genus Megarhinus have been found 

 both within and without bromeliads and are known to feed 

 not only on other mosquito larvse but also on their own 

 species. 



Of all the elements composing the bromeliad fauna, the 

 first is likely to prove most dependent on the host plant. It 

 remains to be determined how far the members of the sec- 

 ond and third elements are limited to bromeliads. Mr. 

 Knab believes that the beetle larvae of the family Cyphon- 

 idae inhabiting bromeliads are distinct species from those 

 which breed in tree-holes and adds, "My belief, in the mean- 

 time, gains some support from the fact that the Diptera 

 breeding in the Bromeliads have been found to be, almost 

 without exception, confined to this habitat." 



Seiior Picado has likened the totality of the epiphytic 

 bromeliads to a great interrupted marsh extending through- 

 out tropical America. Noticing the purity of the water re- 

 tained between the leaves where one would expect foulness 

 from the decomposition of the organic material, he made 

 some chemical researches and experiments from which he 

 obtained highly interesting results. The bromeliads pro- 

 duce a gum which has a digestive action on starches and 

 on nitrogenous materials (albuminoids). The products of 

 the digestion of the vegetable and animal detritus retained 



