THE MICROSCOPE. 37 



tinguishable in such condition from that which causes the vine- 

 bhght and the hop-mildew ; but careful examination will readily 

 show the difference. 



Teeth of Blow-Fly. —In the " Entomologist" for March, 1873, 

 at p. 336, appear some remarks " Oji the Food of Eristalis and other 

 Diptcra^''' which may be cited for the valuable light thrown by them 

 upon the structure of the proboscis of various members of that order: 

 " As to flies, it has been until now generally admitted that they are 

 exclusively destined to fluid nutriment; but in the summer of 

 1867, I was surprised, while observing in my garden an Eristalis 

 tenax upon a flower of (Enothera 7nedia, to discover that it was 

 eating the pollen. Resting upon its middle and hind legs, it 

 thrust out its fleshy proboscis like an arm, seized a morsel of 

 pollen with the two valves which terminate the proboscis, and 

 tote it away from the anther. Since the pollen-granules of 

 CEnothera are tied together by elastic threads, that bit of pollen 

 torn from the anther was attached to others by a band of threads ; 

 and the insect, in order to free its mouth from that inconvenient 

 appendage, began to use its fore-legs. Raising both together 

 towards its mouth, it seized between them the cordon of threads, 

 and rapidly rubbing them one against the other, much as we do 

 in washing our hands, succeeded in cutting the threads and 

 clearing them from its mouth and legs ; then it raised them again, 

 and seized the two valves of the proboscis, thoroughly cleaning 

 them of pollen and the threads yet adhering to it ; and in about 

 three seconds this work of cleaning was complete. At the same 

 time, the valves of the proboscis, by rubbing against each other, 

 had masticated the morsel of pollen, and had conveyed the 

 single granules into the channel of the labium, whence they were 

 pushed into the mouth. It had hardly finished cleaning its 

 proboscis, and eating the first mouthful of pollen, when it seized 

 another portion, and repeated each and all the operations I have 

 described. It was so intent upon its meal, that I was able to 

 observe it in the closest proximity without its manifesting the 

 slightest fear. The quantity of pollen which an Eristalis can 

 devour in this way is surprising. Upon making a section of one 

 and examining the stomach, it appeared very large, and was full 

 of a yellow substance, which consisted of hundreds of thousands 

 of pollen-grains. I have since then had many opportunities to 

 observe this eating of pollen, not only in all the species of 

 Eristalis, but also in the genera Rhingia, Syrphus, Volucella, 

 and Scatophaga. This chewing of pollen alternates with sucking 

 honey, if the flowers have any ; and I am of opinion that the 

 singular structure of the proboscis of flies cannot be fully 

 explained, without taking into account its double function of 



