BEETLES 167 



the salivary ducts ; the mandibular sheaths are open 

 at the back and at their ends, allowing the tips of 

 the mandibles to project freely. A portion of the 

 next pair of mouth-organs, the maxillae, known as the 

 lacinia, is deeply grooved along its inner face, and 

 into this groove the mandible of the same side 

 accurately fits ; the lacinia is of somewhat spongy 

 texture. The way in which these organs are used 

 must be somewhat after this fashion. 



The sickle-like mandibles are plunged into the body 

 of the prey, and as they are forced into the tissues 

 they spring partly out of their sheaths, which remain 

 outside the wound as do also the bluntly pointed 

 spongy laciniae of the maxillae. A secretion from the 

 salivary glands is forced through the mandibular canal 

 into the wound, which serves to make the fluids of 

 the animal's body more liquid, exactly as the Mosquito, 

 preparatory to sucking blood, injects a salivary secretion, 

 which is not only poisonous, causing an abominable 

 irritation round the puncture, but also may contain 

 the micro-organisms which are directly the cause of 

 malarial fever. Outside the wound caused by the 

 Lycostomus larva, the mandible is enclosed in a tube 

 made of two half-tubes the mandibular sheath open 

 at the back and the lacinia grooved down the front ; 

 up this closed channel the juices, rendered more 

 fluid by the salivary secretion, can be drawn into the 

 mouth of the larva. It can be clearly seen from the 

 structure of its mouth-parts that the larva is a suctorial 

 insect, and does not bite or munch its prey. 



After eight to ten weeks the larvae pupate. Immedi- 

 ately before pupation they swell up and become very 

 sluggish. The pupae are white and the outer edges 



