THE MICROSCOPE AND INSECT LIFE 



mouth. The partiality of the house-fly for sugar is 

 well known, and it is interesting to learn how, with 

 its soft fleshy mouth, it can satisfy its cravings. 

 Let us watch one at work on a lump of sugar through 

 our pocket lens. If we look carefully we shall notice 

 that the fly, as he thrusts his proboscis here and 

 there, emits from it a little drop of liquid; after a 

 momentary pause the liquid is sucked up again; 

 it has dissolved a little of the sugar, and the fly 

 enjoys the sugar-laden liquid. 



People frequently state that they have been bitten 

 by a house-fly — a sheer impossibility. What really 

 happens is that they mistake the very similar stable 

 fly for the house-fly. If one of these insects be 

 captured and examined, we shall find not the soft 

 fleshy proboscis of the house-fly, but a cruel look- 

 ing, awl-like mouth easily able to penetrate the 

 human skin. Certain tropical flies, known as 

 Pangonias, have such formidable and lengthy 

 piercing mouths that they can penetrate thick cloth- 

 ing and puncture the skin below. 



Microscopists who care to follow up the study of 

 insects' mouths will know that they are accumu- 

 lating really useful knowledge. Those who do not 

 desire to go so deeply into the matter may well 

 spare a few moments for the examination of the 

 green fly mouth, a needle-like piercing organ which 

 is thrust into plants for the purpose of sucking their 

 sap. The mouth of the gnat is a more difficult 

 subject for the microscopist, though no less interest- 

 ing; it may be compared with the same organ of 



196 



