————— os 
— Me ee ee ee re 
15 
Different species of scale insects undoubtedly behave in different 
manners under adverse climatic conditions, but it is undoubtedly a gen- 
eral and important rule that with them, as with other insects, a cold and 
wet climate is especially unfavorable, also an excessively hot and dry 
climate; and the favorite climate for Coccide is undoubtedly the inter- 
mediate one furnishing plenty of sunshine and warmth with a medium 
amount of moisture. 
The above remarks apply altogether to the effect of summer temper- 
ature and climate; the winter climate as a rule is less important, 
because the insects concerned have become inured to the normal cold 
of winter and hibernate in a condition of growth which best protects 
them from severe freezing cold in temperate climates. 
The excessive cold, however, experienced during the winter of 1898-99, 
aroused the writer’s curiosity as to the ultimate effect upon scale insects, 
and led to an examination of all the local species occurring on out-of- 
door plants available.! 
. Referring to the conditions about Washington, it will be remembered 
that, although well south, the District of Columbia suffered perhaps as 
severe cold as any part of the United States, except perhaps the 
extreme northwest. Unheard-of low temperatures were reached for 
this region and latitude, and many plants were greatly injured or killed 
to the ground which normally winter without any harm from the cold. 
Even peach trees were often completely killed. As would have been 
expected, a great mortality was found to have ensued among scale 
insects, ranging aS a rule above 95 per cent, and in some cases to 100 
per cent. 
Among the seale insects examined were Diaspis pentagona and a 
variety of this species, Diaspis rose, Aspidiotus perniciosus, Aspidiotus 
tenebricosus, Aspidiotus diffinis, Asterodiaspis quercicola, Lecanium nigro- 
fasciatum, Chionaspis pinifoliv, and several species which winter in the 
egg stage. In the case of scales of the latter class, in some instances 
many if not all of the eggs seem to have been killed by the low temper- 
ature. Especially was this true of a species of Prosopophora occurring 
on a variety of A‘sculus growing in the Department grounds. 
The local results described were duplicated, as a rule, in the cases 
of scale infested twigs sent in for examination or identification from 
other localities. 
The only divergent results secured were in the case of Aspidiotus 
ostreeformis, from Geneva, N. Y. These scales seem to have been 
uninjured as a result of the low temperature, but it is possible that 
this is to be explained by the infested plants having been unusually 
protected in some way. 
‘Prof. F. M. Webster in the June Canadian Entomologist (p. 130) has already: 
drawn attention to the fact of the destruction of Diaspis amygdali in Ohio by the 
extremely low temperature reached last winter. 
