MICROSCOPIC OBJECTS. 65 



Fig. 129. Tongue of the House-Cricket (Acheta domestica), 



x 15. 



The tongues of the various insects differ according to the 

 work that they have to perform, as may be seen by examin- 

 ing the descriptions and figures of the various tongues. The 

 common House-Cricket, living chiefly on suction, has a tongue 

 that is well adapted to the purpose, being composed of a 

 quantity of minute tubes, which all join at last into two large 

 ones, which conduct the juices into the alimentary canal. 

 The Crickets are also furnished with strong mandibles. 



The tongue may be dried under pressure, and mounted in 

 balsam ; or it may be mounted in a shallow cell with acetic 

 acid. The last mode of preparation shows the tubes of the 

 tongue best. 



Fig. 130. Water- Scorpion (Nepa cirierea), natural size. 

 Order Hemiptera, Division Heteroptera. 



The insects of this division of the order are chiefly remark- 

 able for having the elytra half membranous and half coria- 

 ceous. The beak also projects from the upper part of the 

 head (see drawing) ; and this beak is characteristic of the 

 order. 



The insect is tolerably common in most ponds. The 

 appendage at the extremity of the insect is used for the inspi- 

 ration of air, and, no doubt, also as an ovipositor. The name 

 Water- Scorpion has been well applied; for its rapacity is very 

 great, as may be found by personal observation. 



The insect, though very thick and coriaceous, may, by long 

 maceration in the potassa, be rendered sufficiently soft and 

 pliable to be pressed between two slips of glass, then well 

 washed, dried under pressure, soaked in turpentine, and 

 mounted in balsam as usual. 



