MICROSCOPIC OBJECTS. 62 



Fig. 123. Antenna of Cockchafer (Melolontha vulgaris), 



x8. 



The antennae of insects vary much as to shape, although 

 the general form is setaceous that is, having the joints 

 gradually diminishing in size from the part that joins the 

 head to the apex. Another form is the lamellate, so called 

 from a number of lamellae or plates joined at their bases ; 

 this form of antennae is chiefly found in the division Lamel- 

 licornes of the order Coleoptera, or Beetles, of which the 

 Cockchafer is an example. Most of the antennae require but 

 little preparation ; to soak them in pure turpentine for two 

 or three days and then mount in balsam is all they require 

 if tolerably transparent. When thickened they must be 

 rendered transparent by the action of the diluted potassa. 



Fig. 124. Leg, with stickers, of the Greater Heater-Beetle 

 (Dytiscus marginalis), x 8. 



The remarkable expansion of part of the leg of this Water- 

 Beetle into a shield, or, as it is called, a patella, will be noticed 

 in the drawing. This peculiarity is only found in the male 

 insect. The tarsus, or foot, is covered with minute suckers 

 or disks, convex in their structure, and often seated on short 

 stalks; there are also generally to be found two or more 

 larger suckers or disks. 



This object may be mounted in an opaque cell; or it may 

 be treated with potassa, washed, dried, and mounted in balsam 

 as usual. 



