io6 THE WONDERS OF INSTINCT 



strange obstacle which stops her as well and interferes 

 with the work of her ovipositor. The cowl inspires her 

 with profound distrust. Despite the tempting bait of 

 the veiled head, not an egg is laid on the wrapper, slight 

 though it may be. 



Weary of vain attempts to compass this obstacle, the 

 Fly at last decides in favor of other points, but not on 

 the breast, belly, or back, where the hide would seem too 

 tough and the light too intrusive. She needs dark hid- 

 ing-places, corners where the skin is very delicate. The 

 spots chosen are the cavity of the axilla, corresponding 

 with our arm-pit, and the crease where the thigh joins 

 the belly. Eggs are laid in both places, but not many, 

 showing that the groin and the axilla are adopted only 

 reluctantly and for lack of a better spot. 



With an unplucked bird, also hooded, the same ex- 

 periment failed : the feathers prevent the Fly from slip- 

 ping into those deep places. Let us add, in conclusion, 

 that, on a skinned bird, or simply on a piece of butcher's 

 meat, the laying is effected on any part whatever, pro- 

 vided that it be dark. The gloomiest corners are the 

 favorite ones. 



It follows from all this that, to lay her eggs, the Blue- 

 bottle picks out either naked wounds or else the mucous 

 membranes of the mouth or eyes, which are not protected 

 by a skin of any thickness. She also needs darkness. 



The perfect efficiency of the paper bag, which prevents 

 the inroads of the worms through the eye-sockets or the 

 beak, suggests a similar experiment with the whole bird. 

 It is a matter of wrapping the body in a sort of artificial 



