84 MORE MINOR HORRORS 



are brought together, and their stiff bristles 

 are run through the brushes as one's fingers 

 run through a beard ; ^ at other times the 

 brushes disappear far into the mouth, and 

 then are slowly withdrawn, passing through 

 the comb-like bristles on the mandibles. The 

 brushes are frequently swallowed, and are 

 withdrawn in little jerks, so that the maxillae 

 have every opportunity of combing any 

 nutritive particles out of them. The whole 

 operation is a most fascinating one to watch. 



As far as one can judge, the currents set 

 in motion by the action of all these forces 

 extend in an area equal to twice the length 

 of the larva, or even more. The currents 

 are in the plane just below the surface-film, 

 and any organic matter lighter than water 

 is swept towards the mouth. In fact the 

 larva sweeps the lower side of the surface-film 

 of the pond or puddle just as a careful house- 

 maid might sweep spiders and flies off a ceiling 

 with a hand-brush. 



The principal food-supply of the larva 

 consists of the spores of fresh-water algae, 

 diatoms, particles of Spirogyra, and any other 

 organisms which do not penetrate the surface- 

 film. Occasionally the larvae devour the de- 

 caying leaves of duck-weed (Lemna), and some- 

 times they attack their dead fellows. 



Grassi found the intestine of the larva 



^ If you have a beard. 



