THE FLY. 43 



LETTER VI. 



THE MOUTH OF INSECTS. — THE PROBOSCIS OE THE FLY.— THE 

 MEMBEES OF LOCOMOTION. — WINGS ; THEIB, STBirCTITRE. — 

 WONDEEFUI, EAPIDITT OF FLIGHT. — HAMBEES OE POISEES ; 

 THEIB ANATOMY AND SUPPOSED FUNCTION. — THE LEGS. — 

 HEMAEKABLB OEGANIZATION OF THE FLY'S FOOT. — EEPE- 

 TITION OF SIMILAE PAETS IN THE OEGANS BESCEIBED. 



Before passing from the consideration of the Ely's 

 headj we have still to examiae another organ, namely 

 that of nutrition, which is termed the proboscis ; this 

 is situated in front, towards the under surface of the 

 head, and when not in use, lies folded up in a de- 

 pression, out of the way of injury. 



In order more clearly to explain the character of 

 this organ, we must briefly describe the typical struc- 

 ture of the mouth of insects generally. Those that 

 masticate their food are usually furnished with the 

 following parts: — 1. an upper lip [labrum), and a 

 lower lip [labium), which work together in a similar 

 manner to our own, and when closed conceal the 

 remaining parts. Between these Hps there is, 3. a 

 pair of jaws {mandibulcB), and, 3. a smaller pair [max- 

 illa), which operate laterally and masticate the food ; 

 and, 4. we find two pairs of feelers ; the first [maxil- 



