JOURNAL, OF ENTOMOLOGY AND ZOOLOGY 43 



EXPLANATION OF PLATE 



Figure 1. Diagram of digestive tract showing position of the proventriculus (P) ; Ms, 

 mesothorax ; Mt, metathorax. 



Figure 2. Portion of proventriculus opened to show the modifications of the chitinous 

 lining. Tl, large tooth; Ts, small tooth; Sp, anteriorly-directed spines; 

 V, valve; Fd, 1, primary fold; Fd, 2, secondary fold. 



Figure 3. Drawing of some of the teeth as seen from the side, showing a group of 

 five large teeth, separated by a small tooth. 



Figure 4. Longitudinal section through the proventriculus [P-P') and oesphageal 

 valve {Oe. ^'. ) ; Oe, oesphagus; Lm, longitudinal muscles; Cm, circular 

 muscles; Ep, epithelium; Ep. col., columnar epithelium; Ch, chitin. 



Figure 5. Cross section through a few teeth in formation showing the cytoplasm {Cy) 

 of the epithelium extending to the apex of the tooth. 



Figure 6. Fully formed tooth. Heavy stippling indicates cytoplasm that has been 

 transformed into chitin. 



Figure 7. Cross section through region of valves. St, stopper; Lm, 1, longitudinal 

 muscle fibres; Lm. 2, longitudinal strands formed by the union of 

 several Lm. 1. 



Figure 8. Cross section through region of oesphageal valve. O, open side of tube. 



Figure 9. Two valves and oesophageal valve dissected out to show that latter is not 

 a closed tube. F, free edge of tube thickened, and bearing chitinous 

 tooth-like projections; CB, dotted line indicates position of circular 

 band of teeth. The folds normally come together, but have been sep- 

 arated in this drawing. 



