FACTS AllOlT WKI.r. KNuWN ANIMALS. !IU 



on a rougher siirfact' likr rlotli or ;i wlatewashod wall, tlicrc 

 will l>e nono.* On such .surlact's the tarsal hooks, by catch- 

 ing in the minutest irregularity, take the ]»laee of the [nvh 

 in assisting the fly's locomotion. 



The other })revalent fallacy is that the smaller flies often 

 noticed in our houses are young flies. In the fly, as in all 

 other insects, real growth takes ])lace only in the larva state. 

 Tt ends with the issuing from the pupa and the expansion 

 of the wings. Individuals diiler in size at maturity just as 

 they do in man and other animals, and various other species 

 of Diptera are often associate<l witli the house-fly, but they 

 arc all full-grown. 



A word as to the fly's parasites. It has several. Probably 

 the most common is the microscopic plant or fungus, {Empma 

 musciv,) which so often sheds a misty halo around it in 

 autumn, and fastens it securely to the window pane; but 

 the title to these remarks excludes its consideration in de- 

 tail. A true internal parasite has been found in the pupar- 

 ium by Dr. Packard, the charactgr of which puzzled him, 

 but which is pi'obably a rove-beetle (family Stapliylinidse) 

 and probably of the genus Oleochara, a species of which is 

 known to be parasitic on an allied genus ( Anthomyia) of 

 flies. The parasite most noticed, however, is the little red 

 mite which so often attaches to it near the base of the wings. 

 Here vou have it when first hatched, (Fig. 10,) and in the 



Fig. lo. — Larva of Trotnbidiutn mtiscarum. (After Riley. ) 



six-legged or Astoma form, having been referred to that 

 genus before its larval character was understood. After 

 attaching to the fly its body swells and its legs get relatively 



* Prof. E. D. Cope mentions that on this principle, even the Amblystoma wc 

 have just talked about climbs a plate of glass with great ease by adhering closely 

 to its surface with the moist abdomen. 



