128 INJURIOUS AND USEFUL INSECTS 



the angle between them the eggs are received as they pass out 

 from the body, and, being sticky, they adhere and form a 

 packet, or egg-raft. When 200 to 300 are collected and glued 

 together, they are set floating on the water. Each egg is of 

 elongate form, and its lower end is furnished with a circular 

 lid, which opens when the larva within is completely developed, 



and allows it to escape 

 into the water. 



The most noteworthy 

 difference between a 

 gnat and a harlequin-fly 

 relates to the mouth and 

 its function. The harle- 

 quin-fly cannot feed at 

 all; the passage from 

 the mouth to the 

 stomach is closed, and 

 there are neither jaws 

 nor any other instru- 

 ments to bite or pierce. 

 But the gnat has a case 

 of slender lancets, and 

 a flexible sucking tube, 

 which enable it to pierce 

 the skin and draw up 

 the juices into the body. 

 It commonly attacks 

 large animals, but is 

 bass of also known to suck 

 caterpillars ; and can 

 be supported for a 

 long time upon ripe 

 fruits, such as bananas. One particular sort of gnat 

 (called Anopheles by entomologists) has recently been 

 convicted of communicating to human beings dangerous 

 malarial fevers of more than one kind. As long ago as 1880, 

 a French surgeon named Laveran observed minute specks 

 in the red blood-corpuscles of malarious patients, and showed 

 that these ultimately enlarged, devoured the corpuscles, and 

 formed rosettes, rounded bodies with minute spheres on their 

 surface. The connection of these bodies with various in- 



Fig. 68. — Mouth-parts of female gnat, 

 antenna ; 7iixp, maxillary palp ; Ire^ labrum-epi- 

 pharynx; I, labium; ;«, mandible; nix^ maxilla; h, 

 hypopharynx. The separated mouth-parts are copied 

 from Dimmock. 



