90 
BRITISH GALLS 
the Continent; the habits of any one species of insect are 
the same everywhere, though it is possible, as the Rev. 
E. N. Bloomfield has pointed out to me, that the insect may 
cause a gall on an allied plant, and in some cases on various 
plants, and the one it favours in Britain may be one on 
which it is not found on the Continent. There are several 
Continental records of homopterous galls on plants which 
find a place only in the alien flora of this country. These 
insects have been recorded as British, and it is possible they 
may have been introduced on the plants in question; but 
until we have certain evidence of their causing galls on 
them in Britain, it is advisable to omit them from the cata¬ 
logue of British gall-causing insects. 
Experimental Galls 
Peyritsch, experimenting with Aphidae in 1888, produced 
modifications of the floral organs, chiefly swollen axis and 
chloranthy, in species of A rabis. The same observer recorded 
that Trioza cerastii H. Low, a species not recorded as British, 
caused a rounded gall consisting of numerous imbricated 
leaves on the stem of Cerastium glomeratum. 
Economic Notes 
The order Homoptera includes some of the most trouble¬ 
some of all pests. The rapidity of production, and the fact 
that its members feed throughout life easily, explain why the 
family Aphidae contains the worst offenders. Several are 
well-known gall-causers, and the majority that have been 
alluded to in this chapter often cause serious losses. Informa¬ 
tion concerning these and many others may be obtained in 
the leaflets issued by the Board of Agriculture, and in Miss 
Ormerod’s “ Manual.” It may be mentioned here that a 
simple method of destroying Aphidae is to spray affected 
plants with a wash made of 10 pounds (or less) of soft soap 
dissolved in 100 gallons of soft water; the soap kills them by 
