4 COLLEMBOLA OF MINNESOTA 



matter makes a kind of scab upon the raw surface of the wound, 

 covering it and enabling- it to heal. These garden fleas feed 

 upon this scab, thus tearing open the healing wound and caus- 

 ing it to bleed afresh. Hereby the holes in the leaf become 

 much larger than they are first made by the flea-beetle, and 

 nature is interfered with and embarassed in her efforts to re- 

 cover from the injuries done by the flea-beetles and other insects 

 which wound the leaves. It is chiefly in this manner, I think, 

 that these little garden fleas are detrimental to the plants on 

 which they occur. Dusting the infested plants with ashes, sul- 

 phur, etc., and most of the other remedies which we resort to for 

 expelling the flea-beetles from them, are still more efficacious 

 in driving off these garden fleas also." Fitch says also of an- 

 other species (Sminthurus arvalis Fitch) that: "It is common 

 to see them in the garden, upon the leaves, particularly of the 

 pie rhubarb. Rheum Rhaponticum, where these leaves are per- 

 perforated with holes by the flea-beetles." I have never met any 

 gardeners in this state who were acquainted with the ravages of 

 these insects, and have never observed them feeding upon green 

 leaves, but the fact that they are known to do so in other places 

 and that they are common here, makes it at least advisable that 

 they should be known and guarded against. 



Sometimes some species of the Aphoruras become very 

 abundant on the surface of water in cisterns and cause consider- 

 able inconvenience and annoyance on account of their great 

 abundance. Of course they are not positively harmful in this 

 case. They are easily killed by pouring a few drops of kerosene 

 on the water. 



From Prof. H. E. Summers, State Entomologist of Iowa, I 

 learned a new fact in regard to their economic relations. This 

 time it was one of the species that lives in the soil that was the 

 culprit. Probably, from the description, it was one of the Ach- 

 orutes. They were very abundant in the soil in which the gar- 

 dener planted some seeds, and kept the soil so thoroughly 

 worked up that the little plants found no chance to root and many 

 of them died. 



Some species of Achorutes might give trouble to the raiser 

 of mushrooms, though I am not certain that they would attack 

 a perfectly fresh mushroom. 



