Vol. xxii] ENTOMOLOGICAL NEWS. 409 



azon. As I passed the cluster of bromeliads around which two 

 females of Mecistogaster modestus were seen flying by us on 

 Thursday, a female of this species was transforming on the out- 

 side of a leaf. I was able to secure both her and her exuvia 

 [8.30-9 A. M.]." "All these observations show that in spite of 

 their unnatural surroundings and perhaps lower temperature, 

 our larvae at Cartago were not retarded in their development as 

 compared with their free relations in their native forest." 



The origin of the bromeliadicolous habit of the larvse of 

 Mecistogaster modestus may possibly be accounted for in the 

 following manner. The majority of the species of Mecisto- 

 gaster are South American and some of them occur along the 

 Amazon, where also are the headquarters of the Bromeliaceae 

 (Wittmack 1888. p. 39). As is well known, "thousands of miles 

 of forest" along this river are inundated in each wet season, 

 so that a person "will travel through this forest for days, scrap- 

 ing against tree-trunks and stooping to pass beneath the leaves 

 of prickly palms, now level with the water, though raised on 

 stems forty feet high." (Spruce, 1908, vol. I, p. 229; Wallace, 

 1853 stc, chap. vii). At such periods of high-water, epiphytes, 

 whether of the Bromeliacese or of other families, would often 

 be just at the water's surface, or only slightly submerged, and 

 would offer to Zygopterous Odonata quite ordinary and usual 

 places for oviposition. An association with certain plants might 

 thus be formed by Mecistogaster or its ancestors, which would 

 persist even when the water-surface was much below the level 

 of the epiphytes. Only such plants as could retain water fof 

 long periods of time (weeks and months) would permit the de- 

 velopment of essentially aquatic larvse and the water must be 

 renewed from time to time. This last condition would prevent 

 the survival of Mecistogaster wherever the rainfall was too in- 

 termittent. Once the association of this insect with bromeliads. f 

 or any other suitable plant, were formed it might persist with 

 the spread of the insect away from the regions of deep yearly 

 inundation (the Amazon or elsewhere), where we conceive its 



t It is suggestive that the legion Pseudostigma Selys, to which Mecis- 

 togaster belongs, and the Bromeliaceae are confined to tropical America. 



