THE ANATOMY OF THE LARVA 43 



seen by the naked eye, and are at this stage so transparent, 

 that ahnost all details of their anatomy can be made out in 

 the living larva placed mider the microscope in a little 

 water. If all superfluous water be carefully removed from 

 beneath the cover, b}^ means of a strip of absorbent paper, 

 so as to slightly press upon without crushing the larva, its 

 naturally vivacious movements will be sufficiently restrained 

 to admit of its being observed at leisure. 



The larvae are easily recognised by their vivacious 

 wriggling movements, as minute worm-like bodies, with a 

 disproportionately large head with a pair of prominent black 

 eyes, and at first sight what appears to be a vertically bifur- 

 cated tail. Being quite unprovided with legs, they swim by 

 means of the strokes of a tail armed with large expansions 

 of bristles. When more closely examined, it is seen that, 

 like the adult insect, it consists of three well-defined 

 regions, the head, thorax, and abdomen. Commencing with 

 the head, it is seen to be not quite so wide as the thorax, 

 bat considerably wider than the abdomen, and forms a 

 truncated cone, wider than it is long, and separated from 

 the thorax by a distinct sulcus. It is ornamented on the 

 dorsum with several patches and lines of pigment, the 

 arrangement of which, however, is not very constant ; and 

 at the broadest part laterally are placed the two large 

 eyes. It is further ornamented m various places with tufts 

 of strong bristles, the structure of which is often very 

 complex. 



From two slight prominences a little in front of the 

 eyes spring the antenna^ and projecting from the middle 

 of the anterior border of the head may be seen a complex 

 arrangement of bristles springing from the upper lip and 

 mouth parts. 



The greater part of the upper surface of the head is 

 formed by the dorsal surface of the third metamere. In 

 front of this is the clypeus or dorsal plate of the second 

 metamere, a short but broad plate, with a shallow, curved 

 indentation in front, while laterally it is armed with a pair 

 of incurved tufts of bristles which form what Meinert (De 

 Encephale Mygelarver) speaks of as a whorl, or rotatoi-y 



