A correspondent from Allegheny, Pa., sent us some insects a few months ago, which in a note in the Monthly we said might be the ordinary Black fly or Aphis of greenhouses. There were only a few, and fast to the bottom of the bottle, and we could not get them out without filling with water, and shaking them up and out. We understand that another florist, afflicted by what he believes the same insect on smilax, sent a few to Prof. Riley, who pronounces them a species of Haltica, an ally of the turnip fly. Tobacco smoke would hardly destroy these, as they would fall to the ground where the smoke would not be dense, and come up again. Prof. Riley says insect powder is the best remedy.