MUSCA TENAX. 319 
Mother, The tail is formed of two 
iwbes ; that next the body being the 
largest, and into this the animal can 
draw the smaller tube, which forms the 
farther half of the tail. 
Lucy, Then I suppose they keep the 
tip of the tail above water, like the larva 
of the chamelion fly, and that it is for 
that purpose they are enabled to alter its 
length ? 
Mother, Yes ; they lengthen or short- 
en their tail according to the depth of 
water ; and not only by pushing out the 
smaller tube to its full length, but also by 
extending, or stretcliing, both the tubes, 
which are as elastic as a thin piece of 
Indian rubber. 
Lucy, These little creatures do not 
seem to have any filaments at the end of 
the tail, like those of the fan-tailed 
larva. 
Mother, Yes, they have; the tail 
ends in a fine point, from which proceed 
five hairs, that spread out upon the sur- 
