: PLATE XXX. 



CORIXID MOUTH PARTS AND DIGESTIVE TRACT. 



Fig. 1. The digestive tract of a Corixid, showing the long green fila- 

 ment of algae which it had eaten. Sometimes the boatmen fill their 

 stomachs with great skeins of Oscillatoria. (The above drawing was 

 made from a permanent slide, the green color being preserved by 

 fixation in 8% formalin plus copper acetate.) 



Fig. 2. The tip of the so-called rostrum of a large species of Corixid. 

 The median stylets and one lateral stylet (in black) are shown project- 

 ing from the small oral opening (o). This opening is bounded by the 

 membrane (m), which is provided with the chitenous trusses (I). These 

 trusses are attached to the muscles (mu). Thus when the muscles con- 

 tract the oral opening is considerably enlarged. 



Note the projecting, somewhat spoon-shaped guards, below (g). When 

 the palae of forelegs sweep downward across the face these concave shields 

 help to keep the food from passing beyond its objective. 



Fig 3. Digestive system of a Corixid. The inner surface is increased 

 by diameter instead of by length. There are four malpighian tubules. 

 This drawing is from the mount of the digestive tract of a bug that had 

 fed for a few minutes over some sediment lightly sprinkled with carmine 

 grains. Quantities of carmine were swept in with the organic ooze. 



Fig. 4. Ventral enlarged view of mouth parts dissected. The man- 

 dibular stylets are on the outside. 



Fig. 5. Dorsal or cephalic view of mouth parts. 



Fig. 6. Stylets enlarged, 

 a. right inner stylet. 

 h. left inner stylet. 

 c. left outer stylet. (See, also, figure 5.) 



Fig. 7. Shows left inner or maxillary stylet (6) and right outer or 

 mandibular stylet. 



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