188 PLANT LICE. 
difficulty is in the application. The lice get under the leaves or 
curl them, and the spray does not reach them. The remedy is 
to use the modern machinery for applying the insecticides. For 
spraying insecticides on cabbages, a knapsack sprayer is necessary, 
and to this a Cyclone or Vermoral nozzle should be attached. 
This nozzle, at the end of a stick of convenient length, can be 
passed all around and into the cabbage plant, sending a fine spray 
into every corner. A man can go over a large field, stopping 
only a few seconds at each plant and wasting no liquid. The in- 
secticides should be applied as soon as the lice appear in any 
numbers.” (Smith). 
Aphis rubicola Oest. (The Smallest Blackberry Aphis). 
This sometimes occurs in large numbers on the under side 
of the leaves of Rubus strigosus. According to Oéestlund it 
should be easily recognized from our other species on account 
of its small size and its simple sensoria. 
Aphis rumicis Linn. (The Bean Plant-louse). 
This is a rather common dark or aerial plant-louse infesting 
the garden beans; in some cases it is very destructive to certain 
kinds, forming black rings around the flowering heads. The 
writer has repeatedly tried to introduce a large bean from Europe, 
but failed to make the plants bear although they would flower 
in abundance. Even after introducing the root-bacteria of this 
plant, which form very large gall-like swellings on the roots, he 
failed, simply because the lice infested the bean-plants to such 
an extent as to dwarf the pods. This was very peculiar, as the 
plant had never been grown in the state, and the question arose 
whence came the lice. It seems however, as if the same species 
occurred also on such weeds as the Chenopodium, and Rumex. 
Prof. Osborn gives the life-history of this species in one of 
his reports, and as his conclusions are not alone very interest- 
ing, but also important, to gardeners and fruit-growers, they are 
quoted: 
“The question naturally arises of what economic value is 
the life-history of an insect, especially a plant-louse; which some 
florists distinguish as ‘Green Aphis’ and Black ‘Dolphin.’ 
“Many people have undoubtedly observed the sudden disap- 
