JUKE. 145 



one author, comprising technical descriptions of a portion 

 only; one genus contains 315, and another 230 species. The 

 legs of the Muscida, like those of other Dipterous insects, 

 are terminated by a tarsus consisting of five joints, the last 

 being armed with two claws and furnished with lobes, which 

 enable the insect to perform the curious, though common, 

 feat of walking with the back downwards on the ceiling, and 

 on highly polished substances. It has been generally sup- 

 posed that this was effected by the formation of a vacuum, 

 caused by the close application of the margin of these lobes, 

 and the muscular rising of the central parts ; but Mr. Black- 

 wall, in a volume of the Linneeau Transactions, has sug- 

 gested a new solution of this interesting point. He says, 

 that after much research into the subject, and many ex- 

 periments, he breathed into phials containing Flies and 

 other insects capable of walking in this manner, and found 

 that when flie moisture was condensed on the surface, it 

 totally prevented the insects from taking hold of the glass ; 

 the same ensued when a little oil was substituted, or flour, 

 pulverized chalk, etc., which adhered to the lobes of the 

 foot. These facts seem to imply that an adhesive secretion 

 is emitted by the instruments employed in climbing, and 

 this, by the aid of highly magnifying powers, was found to 



