jiungerford: aquatic hemiptera. 241 



in demonstration for a long time. For detailed studies of di- 

 gestion the usual histological methods must be followed. 



SPECIAL STUDIES. 



Carmine Feeding. 



As stated under the heading of general habits, the use of 

 the flat palae of the fore legs in feeding is easily observed. It 

 occurred to the writer that if powdered carmine were sprinkled 

 over the sediment on the bottom of the aquarium it might be 

 taken up by the boatmen in their feeding and serve as an index 

 to the time it takes for food to pass through the digestive 

 tract. If found in the stomach in large quantities it would add 

 further evidence to the belief that they scoop the food into the 

 mouth in quantities. Several experiments and demonstrations 

 have been made by placing the powdered carmine upon the 

 sediment in the bottom of the jars and then turning in Corixids 

 to feed. If hungiy the boatmen will begin at once, and a dis- 

 section of one of them after ten or fifteen minutes feeding will 

 prove that they take up the carmine and organic ooze in 

 quantities. The digestive tracts have been found packed from 

 end to end with the red material. On plate XXX is given 

 a figure in color of the digestive tract of a Corixid after 

 feeding upon carmine covered forage. Permanent mounts of 

 digestive systems in balsam make useful slides for demonstrat- 

 ing this point, since the walls of the stomach become clear and 

 the red material within gives striking preparations. 



This carmine-feeding experiment was attacked from every 

 angle in order to avoid drawing any false conclusions. A care- 

 ful reading of the notes obtained will indicate how easily one 

 could fall into errors hy superficial examinations. The experi- 

 ment was planned and executed by the following outline : 



Typha Culture 17129. 



A. Survey of culture. 



B. Stender with culture and carmine. 

 a. Survej' culture after 24 hours. 



h. Place Corixids here that have been in clear water for 24 hours. 



1. Forage 1 minute and examine. 



2. Forage 5 minutes and examine. 



3. Forage 20 minutes and examine. 



4. Forage 20 minutes, remove to clear water for 30 minutes and 



examine. 



5. Forage 20 minutes, remove to clear water for 130 minutes and 



examine. 



16 — Sci. Bui. — 1669 



