AUTUMN NUMBER 25 
time to apply the fungus is when the maximum number of crawl- 
ers are out, i. e. about a week after the culmination of the June 
flight of adults. The yellow aschersonia, however, should ac- 
cordingly, be applied about the middie of July. The same prin- 
ciple applies to the scale-infesting fungi. They should be sprayed 
on the trees when the maximum number of scale crawlers are 
out. 
Mr. A. C. Brown spoke on sweet-potato certification. 
The committee on truck crops reported the control of aphids 
to be one of their most serious problems. 
RELATION OF ENVIRONMENTAL FACTORS TO WING 
DEVELOPMENT IN APHIDS' 
By ARTHUR C. MASON 
The generally accepted theory of most entomologists and 
experimenters on the subject is that winged forms of aphids are 
produced only when the continued existence of the apterous 
forms, under conditions then existing, might prove disastrous 
to the species. This occurs always in the fall in cold climates 
when sexual forms are produced, the males of which are usually 
winged, and also at any migrating season in the case of those 
species which live on two or more different host plants. There 
are also many other causes attributed to these adaptive varia- 
tions. Among the factors which may be potent in acting as 
effective stimuli for wing formation are crowding on the host 
and hence lessening of the food supply, unusually high or low 
humidity, early lowering of temperature in autumn, changing 
constitution of the sap of the plants by chemical means, etc. 
In collecting aphids it was noted that usually both winged and 
apterous forms occurred in’ the same colony; also, in the life 
history work with Myzus persicae, that some of them would be 
winged and others apterous. In several cases plant lice which 
were apterous when collected would develop wings when kept in 
the laboratory for a day or two. The question often arose as to 
why some of these forms were winged and some apterous when 
living under the same conditions, and as to whether the en- 
vironment of the aphids in the breeding jars had an effect on 
this. Hence a series of experiments was planned to prove or 
disprove some of these theories. 
1A synopsis of Part III of thesis entitled “Systematic and Biological Studies of 
Some Florida Aphididae’, presented by the writer in 1915 to the University of 
Florida for the degree of Master of Science. This is the third and concluding paper 
of the series. 
