Objects for t/ie Microscope. 95 



easily obtained as the foot of Syrphus, it should by all 

 means form part of an educational box. 



The Syrphus is one of those flies which vibrate over our 

 flowers in the summer, and haunt the Michaelmas Daisy 

 in the autumn. They are called Drone-flies and Wasp- 

 flies, and are mistaken sometimes for one of the Hyme- 

 noptera. 



This foot displays that pair of membranous expansions 

 called pulvilli which enable the fly to walk up and down 

 smooth surfaces, on glass and on ceilings, in opposition to 

 the laws of gravity. They are fringed with minute hairs, 

 each of which is tubular, and secretes a viscid fluid which 

 attaches the foot to the surface of the glass or wall, and the 

 hooks on either side act as fulcra or props, with which the 

 fly pushes against the substance when it desires to detach 

 itself. The joints above the pulvilli are called tarsi. 



LEG OF DYTISCUS, OR DTTICUS. 



A most splendid object for the polariscope. The Dytiscus 

 is a large water-beetle, common in ditches and ponds, and 

 this is the fore-leg of the male. That large round disc is 

 composed of three joints of the tarsi, which are studded 

 with suckers ; one is extremely large, furnished with radi- 

 ating fibres, and another is somewhat smaller, with single 

 cup-like suckers raised on stalks, altogether giving it an 

 immense power of adhesion. 



FOOT OF WASP, 



another favourite object for the polariscope: the tarsal 

 joints are well seen, as also the hooks on each side of the 

 pulvillus. 



FOOT OF OPHION. 



These toothed claws belong to an Ichneumon-fly (Ophion), 

 which deposits its eggs in the larva or caterpillar of a moth 

 (Bombyx Vinula, Puss Moth). The fly is yellow and has a 

 sickle-shaped body, the ovipositor slightly exserted. (See 

 Hymenoptera Microgaster.) 



