388 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1952 



a bromeliad breeder, the factors of the infestation became evident. 

 Later some interesting observations by Pittendrigh (Downs and 

 Pittendrigh, 1946, 1949; Pittendrigh, 1950a) showed why bellator was 

 mainly responsible. The climate in the forest varies regularly from 

 the ground to the treetops and plant and animal life is zoned accord- 

 ingly. A mosquito species like Anopheles homunculus that breeds 

 near the ground finds few bromeliads so that its numbers are relatively 

 small, and outside conditions are such a contrast to its constantly 

 dark and moist habitat that it leaves the forest only under extremely 

 humid conditions. A. bellator, on the other hand, is concentrated 

 near the top of the forest where the great mass of bromeliads offers 

 excellent breeding grounds. The dry sunny climate offers less con- 

 trast to nonforest areas and consequently bellator leaves the forest 

 readily to attack man (fig. 1) . 



The center of the infestation was in the cacao plantations, the back- 

 bone of Trinidad agriculture, so that this time man had brought the 

 forest and its mosquitoes to him rather than entering it, like the men 

 in Lutz's studies. Cacao planting in Trinidad involved setting alter- 

 nate rows of cacao and quick-growing immortelles {Erythrina glauca 

 and E. poeppigiana) , the latter to give the cacao plants necessary 

 shade. Bromeliads from the nearby forests invaded the plantations 

 like weeds and found particularly favorable perches on the immor- 

 telles, covering them in profusion. With the bromeliads came swarms 

 of mosquitoes that until now had been too remote in the forests to 

 act as carriers. However, in the plantations they came in contact 

 with the workers living there and the disease shortly developed to 

 crippling proportions. 



Local health authorities and the scientists of the Rockefeller Founda- 

 tion set out to control the disease and soon found that previous experi- 

 ence with malaria was of little help. The usual ditching and draining 

 procedure was completely useless against a carrier that bred above 

 ground. Cutting down the trees would have solved the health problem 

 but would have been economically ruinous. 



In Trinidad, bellator spends little time in houses (Downs and 

 Pittendrigh, 1946), so it had to be eliminated in its natural habitat 

 and the best way appeared to be by removing its bromeliad breeding 

 places. Given the short flight range of the mosquito, it seemed possible 

 to protect the cacao workers by clearing the bromeliads from the 

 plantations by hand. Crews went to work pulling the bromeliads off 

 the trees, but it was soon evident that progress was too slow to make 

 appreciable headway against the disease. Meantime studies of the 

 bromeliads had shown that even the commonest species differed 

 greatly in their receptivity to mosquitoes. Gravisia aquilega and 

 Aechmea nudicaulis were of almost identical frequency, yet the 



