122 ENTOMOLOGICAL NEWS. [March, ’08 
Winged Aphids, 
C. W. WoopwortH, Southern California Pathological 
Laboratory, Whittier, Jan. 17th, 1908. 
In the course of a study of the cabbage aphis, Aphis bras- 
sicae, it was noticed that the wilting of the plant resulted in 
an immediate slowing down of the birth rate. This season has 
thus far been unusually dry in the southern part of the State, 
and in almost all fields there have been innumerable cases of 
evident diminution in the number of aphids without much 
parasitism or sign of fungus or bacterial diseases. A leaf 
badly curled and almost entirely covered on one side by the 
aphids first shows a spontaneous production of young. with 
wing pads. When these young have become full grown they 
fly away and the leaf becomes ultimately entirely free from the 
insects, except perhaps the bodies of a few swollen up parasi- 
tized individuals that may still remain and the cast skins that 
sometimes cling to the surface. 
There may be some connection between these two observa- 
tions, since the failure of plant licé to develop wings under 
more favorable conditions may be due simply to the rapidity 
of development of the rest of the body. After about one day 
from the birth of plant lice, those that are to produce wings are 
clearly distinguishable. Possibly the delay before birth result- 
ing from a partial wilting of the plant, or possibly the short- 
age of food for the new-born insect may give the wing buds 
time to begin development and to reach a point where they 
have an even chance with the other organs of the body. 
_ Professor Clarke has shown* that the common rose aphis, 
Siphonophora rosae, can be made to produce wings in the first 
generation upon rose cuttings in sand wetted with solutions of 
magnesium salts, while nothing else tried showed any effect. 
This is a case where there is no diminution in water supply; 
either the wing buds were stimulated by the presence of mag- 
nesium, or the other parts of the body were retarded. li the 
latter is true, it would simply fall in line with the suggestion 
made above. 
* The Journal of Technology. Vol. 1. 
