ENEMIES OF APHIDES. 397 



The Mandibles and Maxilla. 



The mandibles of this larva, as shown at Fig. 2, are corres- 

 pondingly shorter and thicker than those of the Chrysopa larva, 

 shown on PI. XII., and are provided towards the apex with three 

 or four denticulations, well adapted from their shape to prevent the 

 escape of prey, when once pierced. Lower down, the inner edge 

 is finely serrated, but the value of this is far from evident, the 

 mandible being rarely inserted in the body of a victim to any 

 depth. 



The hollow-grooved shape of the mandible is well displayed in 

 this specimen. At Fig. 3, on the same Plate, is shown the 

 maxilla withdrawn from the mandibles. The transverse opening 

 at the extremity, through which the juices of the aphis are sucked, 

 is very evident, and a long fold or groove down either side simu- 

 lates very closely a longitudinal continuation of the slit, but a 

 careful examination reveals its true nature. 



It has been stated by some writers of authority that the maxillae 

 are so shaped as to simply close the groove of the mandibles, so 

 that the two together form a hollow tube, which acts as the channel 

 to the oesophagus at their base. I have been unable to find any 

 evidence to confirm this view, and after frequendy watching under 

 the microscope the action of larvae in abstracting the juices of 

 aphides, I cannot doubt that the latter enter the tubular and 

 greatly modified maxillae by the narrow opening at their extremity, 

 and pass downwards by the suctorial action of the oesophagus into 

 that organ. The action of the mandibles is, in my opinion, limited 

 to the purposes for which their structure adapts them — the piercing 

 the skin of the victim, and affording a safe passage for the action 

 of the maxilloe, which they protect. Anyone who will take the 

 trouble to watch a larva seize and destroy an aphis under an inch 

 or half-inch objective, which may readily be done by confining the 

 insects in a shallow cell, will almost certainly deduce, from the 

 movement of the maxillae and the downward passage of the 

 ingested oil-globules from the aphis, that the function of the man- 

 dibles themselves is merely that of a weapon and a sheath. 



The entire absence of any opening at the superior end of the 

 oesophagus, answering to the ordinary nature of a mouth, is one of 

 the most curious features of the Neuropterous group to which the 



