254 



FLASHLIGHTS ON NATURE 



LA. 



MP 



true flies still retain, in most cases, the two tiny 

 poisers or balancers, just to remind us of their 

 descent from four-winged ancestors. Nature has 

 no habit more interesting than this retention of 

 parts long since disused or almost disused ; by 

 their aid we are able to trace the genealogy of 



plants and ani- 

 mals. 



In No. 1 1 we 

 have a dissec- 

 ted view of the 

 mouth-organs 

 and blood-suck- 

 ing apparatus 

 of the gadfly, 

 immensely en- 

 larged, so as to 

 show in detail 

 the minute struc- 

 ture. In life, 

 all these separate 

 parts are com- 

 bined together 

 into a compound 

 sucker (com- 

 monly called the proboscis), which forms practi- 

 cally a single tube or sheath ; they are dissected 

 out here for facility of comprehension. The longest 

 part, marked LA in the sketch, is the labium or 

 lower lip, which makes up the mass of the tube ; 

 it ends in two soft finger-like pads, which are fleshy 

 in texture, and which enable it to fix itself firmly 



NO. ii. THE GADFLY'S LANCETS, WITH 



OTHER PARTS OF THE PROBOSCIS. 



