PROTOZOA OF LATEX PLANTS 267 



If a colony of infected insects is desired, a number of individuals 

 are isolated and fed on infected plants of Asdcpius for a few days. 

 Some of them will become infected from this feeding; but if it 

 is desired to infect all of the individuals prolonged feeding on 

 infected plants may be necessary. 



Dry seeds are better food material than moist seeds because 

 they remain in perfect condition for weeks without sprouting or 

 rotting as wet seeds tend to do. The insects seem to be able to 

 utilize moist or dry seeds equally well. In feeding, the insects 

 place their beaks in the seeds and remain quietly in position 

 for some minutes, finally pumping vigorously. Apparently they 

 digest their food before ingesting it, a process for which the 

 large amount of saliva present in their salivary glands must be 

 useful. The same process has been watched when an adult has dis- 

 covered an ^gg and attempted to suck it. First the beak is care- 

 fully adjusted within the ^gg. Then a period of several minutes 

 intervenes in which the tgg is entirely normal in appearance. 

 Presumably during this period it is being digested by the salivary 

 fluids. Suddenly the insect becomes restless, shifts its position 

 slightly, begins a pumping motion, and within a few seconds 

 empties the entire tgg, which changes from its completely normal 

 appearance to that of a thin papery shell, its hitherto turgid 

 walls collapsing rapidly. The large amount of saliva needed for 

 this process of feeding may account for the need shown for a 

 constant supply of water. If water is not readily available the 

 insects sometimes kill and suck each other. It is therefore im- 

 portant to maintain an adequate supply. If a colony has been 

 deprived of water for a few hours the insects become flattened 

 in shape and dull in color. When water is supplied they drink 

 greedily and soon expand, becoming glossy individuals again. 

 The water tube described above serves this purpose well. The 

 insects find the small opening and congregate around it to drink. 



Staining latex protozoa. Another special method in the study 

 of latex flagellates is that of fixing and staining microscopical 

 preparations. Latex flagellates are distorted by drying in thin 

 smears, and if dried must usually be examined in thick smears. 

 The most convenient way to detect flagellates in latex samples 

 from large numbers of plants in the field is to use a quick stain 

 which is not sufficient for cytological study, but is useful for 

 preliminary work. Alany smears of latex can be collected in the 



