THE HOUSE FLY 41 



hatches out into a grub which feeds upon the juices of the fly 

 maggot or the chrysalis, and anon issues forth as a winged 

 insect, having devoured its host. This may be observed 

 by anyone with Ichneumon Flies. The female seeks out 

 a caterpillar of a butterfly or moth, and, puncturing the 

 skin with her ovipositor, lays one or more eggs in her host. 

 These eggs hatch out into grubs which feed upon the 

 internal juices of the caterpillar. The latter, however, does 

 not die until it changes into a chrysalis, otherwise known 

 as a pupa. By this time the grubs of the Ichneumon Flies 

 are full grown and also change at the same time into 

 chrysalides and, behold ! instead of a beautiful butterfly 

 or moth emerging from the chrysalis, half a dozen or more 

 Ichneumon Flies issue forth and fly away. 



Amongst reptiles, our greatest allies are lizards. All 

 the smaller lizards greedily devour flies and other insects 

 noxious to man. The chameleon is the finest fly-catcher 

 of all its reptile brethren. It has been specially evolved 

 to keep flies in check. The tongue is bulbous and sticky 

 at the point, and lies contracted within the chameleon's 

 mouth. Advancing silently hand over hand on a twig, 

 it stalks a fly, and when about six inches from it, the 

 chameleon pauses. The mouth is seen to slowly open, 

 the careful watcher imagines he sees a momentary flash, 

 and notices the fly has vanished. What occurs is this : 

 the chameleon shoots out its tongue, and the aim is so 

 unerring and so exact that the sticky tip of the tongue 

 merely touches the fly, which adheres to it and is with- 

 drawn into the chameleon's mouth and swallowed. The 

 chameleon can shoot out its tongue to a distance averaging 

 from six to nine inches. 



