Objects for the Microscope. 123 



a beautiful lower lip or labrum, used first for steadying the 

 lancets in their descent through the skin, and then for 

 sucking up the fluid. This may be watched by any one 

 who will permit this little Gnat quietly to take a meal on 

 the hand ; and once fixed she is not easily alarmed, but 

 will allow the approach of a pocket lens, and observation 

 of her proceedings. 



The Diptera have also a tongue (lingua) ; it is not the 

 organ usually so called, but a lancet, which with four 

 others lie concealed within the horny lip or labrum of 

 Tabanus. The part we so much admire in the proboscis 

 of the Blow-fly, Tipulae, and others, is the lower lip or 

 labium, with its lobes striated by radiating tracheae. 



The head of a fly is attached to the thorax by a very 

 slender neck, and appears to move upon a pivot, having 

 the power of turning quite round. 



The thorax is compact, and gives support to the wings, 

 halteres, and three pairs of legs. 



The abdomen is composed of from five to nine segments, 

 and females are provided with ovipositors, sometimes of 

 great length, and consisting of a series of little tubes 

 sliding one into another like a telescope. 



The legs have always five tarsi, two claws, and two or 

 three membranous lobes, or pulvilli. Of the internal ana- 

 tomy of flies I must not allow myself to say much ; but it 

 may interest many to know that they possess the dorsal 

 vessel or heart which ensures the circulation of blood, an 

 alimentary canal for the digestion of food, provided with 

 salivary vessels, biliary tubes, and a chylific stomach which 

 seems to supply the whole intestinal canal with a power of 

 digesting food when necessary. Flies have a crop or gizzard, 

 situated just above the stomach, and appended by a long, 

 narrow neck to the throat or oesophagus ; but it is used 

 chiefly as a reservoir for food, when the insect takes more 

 than is needful for its immediate wants. This was proved 

 by that great anatomist, Hunter, who kept a fly twelve 

 hours without food, and then gave it milk and killed it ; he 

 found no milk in the crop, but it had got through almost 

 the whole tract of intestines ; the animal had immediate 



