E. Hargrbaves 307 



mandibles of other insects. The mandibles are outside (lateral to) the 

 maxillae, which are fused along their length, forming by their union 

 two ducts — a small posterior one for the passage of the saliva from the 

 salivary pump to the leaf, and a larger anterior one for the passage of 

 the food from the leaf. In the dorsal (anterior) wall of the pharynx 

 is the cribriform organ, to which is assigned the function of tasting the 

 food (sap) as it enters the mouth. The arrangement of the mouth-parts 

 is similar in all the stages. 



When the larva inserts its stylets into a leaf, in all the cases I have 

 observed (by means of sections of leaves with the larvae in situ), the 

 stylets go to the phloem cells of the vascular bundles, which contain 



Fig. 8. Larval stylets in the leaf tissue. 



proteids and albuminous materials — obviously the most suitable 

 destination (Fig. 8). The entire sucking apparatus (viz. stylets, sali- 

 vary pump, and chitinous structures in connection with them) is capable 

 of a slight backward-and-forward movement, and this is the case in 

 the next three instars also. As to the stylets themselves, they have 

 a regular cycle of movements (Fig. 9), which is as follows. The man- 

 dibles (outer stylets) are thrust forwards (outwards) simultaneously, 

 sliding on the maxillae (inner stylets). Their tips are incurved. They 

 are then withdrawn one at a time, their curved ends scraping against 

 the tips of the united maxillae, as if to bring food towards the latter 

 to be sucked up. 



Ann. Biol, i 21 



