212 THE CANADIAN ENTOMOLOGIST 



planed board, a papered wall, or a velvety fabric, and you will experience- 

 much greater adhesion to the smoother objects, and may understand the 

 important part which these moist pads play in the locomotion of the fly. 

 They also act, in part, like the cushions of a cat's paw in protecting and 

 preventing abrasion of the claws, which are very useful on the rougher 

 surfaces, where the pads are less serviceable. 



Now, compared with Musca doniesfica, the claws of Siurop/iaga sarra- 

 ceiiicc are much the longest and strongest, and the pads much the largest, 

 presenting three or four times the surface. These difl'erences are, I think, 

 sufficient to explain the fact that while the common fly walks with 

 slippery and unsteady gait on the smooth pubescence (the retrorse nature 

 of this pubescence sufficiently explaining the downward tendency of the 

 movement), its sarcophagus congener manages to get a more secure 

 footing ; for not only does the latter present a larger adhesive surface, but 

 the longer claws are more likely to reach beyond the pubescence and the 

 bristles, and fasten to the cellular tissue of the leaf beyond. Moreover, 

 Sarcophaga is more thickly beset with stiff, spinous bristles than Musca, 

 and Dr. Mellichamp says that when disturbed it buzzes violently about, 

 just as if an animated sheep-bur had fallen into the tube — not apt to go 

 down, because it will hitch and stick, and finally, by main force, it 

 generally emerges, but once in a while also succumbs. 



In answer to the second question I can only say that there is nothing 

 exceptional in the power of the larva to withstand the solvent quality of 

 the fluid ; it is, on the contrary, in accordance \\\\\\ the facts known of 

 many species of Muscidse and Qistrid?e, some of which, like the well-known 

 horse bot, revel in a bath of chyme, while others are at ease in the 

 intestinal heat of other warm-blooded animals. It is also well known that 

 they will often live for hours in strong liquids, such as alcohol and tur- 

 pentine. 



In answer to the third question, the moth is doubtless assisted in 

 walking within the tube by the spines and spurs on the legs, which it, in 

 common with most other moths, possesses — the tarsi in Xanthoptera 

 being armed with spines, and the spurs being quite long, and in sciiiicrocea 

 usually shod at tip with a corneous point. Its larva overcomes the 

 treacherous surface by either carpeting it with silk or destroying it. 



CONCLUSION. 



To one accustomed to seek the why and wherefore of things, the 

 inquiry very naturally arises as to whether Xanthoptera and Sarcophaga 



