338 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



ing adults. It consisted of an open bamboo node, one or both ends of 

 which were replaced with fine screening (pi. 21, fig. i). A longi- 

 tudinal section was cut off one wall and it, in turn, had its midregion 

 cut out so that it formed a frame. This open region was covered with 

 screening which had a single outlet over which a vial was held in place. 

 The apparatus was stocked with leaves containing eggs, larvae, and 

 pupae and then arranged in any body of running water so that the 

 current passed through one end of the node and came out the other. 

 When adults emerged they would be attracted by the daylight entering 

 through the screening on the upper surface of the structure, and would 

 work their way through the outlet into the vial. This system was 

 not very practical in the streams of the Yepocapa regions since the 

 bamboo node soon was filled with sand which killed the larvae and 

 pupae. 



However, the problem was not to rear adults, but rather to establish 

 a self-perpetuating colony. With this in view, during the last half of 

 1948 a large outdoor screen cage, 8' x 6^' x 5', was constructed in 

 the laboratory patio over a cement channel through which a stream 

 was diverted. Some of the plants found in and about the natural 

 haunts of the flies were planted within the cage. These were : banana, 

 coffee, Grevillea robusta Cunn., Ricinus communis L., and Polymnia 

 maculata Cav, Two herbaceous plants on which the flies commonly 

 oviposit in this region, Renealmia aromatica (Aubl.) Griseb. and 

 Tradescantia commelinoides R. & S., were planted along the borders 

 of the stream in such a manner that the leaves and stems floated on 

 the surface with the current. Temperature and humidity within the 

 cage fell well within the natural range of the region. The mottled 

 shade and sun, usually found on the coffee plantations, was approxi- 

 mated by attaching lengths of rather sheer black cloth to the outside 

 of the cage where the sun hit directly. This reduced light intensity, 

 and the movement of the cloth in the air currents afforded additional 

 aeration of the interior of the cage. At a later date an exhaust fan 

 was installed in the roof. 



Many combinations of flies were introduced into the cage: wild- 

 caught females, wild-caught females with laboratory-reared males, 

 laboratory-reared females and males, and females and males reared 

 in artifacts in the field. Pupae were also introduced into the water 

 channel so that the adults could emerge naturally within the cage, thus 

 reducing unnecessary handling. The foods presented to the flies were 

 human subjects, defibrinated human blood, blood plasma, plant juices, 

 mashed banana or raisins, and honey and sugar solutions absorbed 

 by cotton. 



