88 THE FLY. 



there may be no confusion in the sight of the fly, though the 

 image is seen by several lenses at once. Besides these large 

 compound eyes, there are on the crown of the head three 

 small and simple ones, called ocelli. 



The proboscis of the house-fly is bi-lobed at the ex- 

 tremity, and adapted for sucking only. There are no lancets, 

 as such, but between the two lobes there are three rows of so- 

 called teeth, which may be used on occasion to triturate sugar 

 and such-like food. The proboscis of the Blow-fly only differs 

 from that of the House-fly in being larger. Its interest and 

 beauty have made it the most popular object for the micro- 

 scope. While looking at it there will be seen two club-shaped 

 appendages with short bristles about them. They are supposed 

 to be organs of taste, and are called palpi. Whilst flies have 

 only two, other insects have four of these organs. 



The connection between the head and the thorax is by a 

 pedicel of small diameter. The wasp, one of the enemies of the 

 fly, would seem to know this ; for in his attacks, his first effort is 

 to bite through this, which he does easily. Twice has the writer 

 seen this done, and the fly rendered helpless by the loss of its 

 head. 



Turning to the thorax, the first organs to attract our notice 

 are the wings, which are membranous, having lines running along 

 them, called nervures. These, and the spaces between them, 

 are severally named ; being found useful in separating flies into 

 families. The wings are set in motion by very powerful muscles, 

 and make an extraordinary number of vibrations in a short 

 space of time ; one authority says, six hundred in a second, 

 and that one-third of a] mile can be traversed in a minute. 

 Another authority tells us that the wings make a little over twenty- 

 one thousand vibrations in a minute. These produce the musical 

 note "i^," which is known to require this number of vibrations, 

 and thus the number is ascertained. 



The legs are five-jointed : the last joint of these, called the 

 tarsus, or foot, being also five-jointed. At the extreme end are two 

 claws, likened to rams' horns, and two pads covered underneath 

 with short hairs, which are hollow. It is these hairy pads 

 which enable the fly to perform the wonderful feat of walking 



