INFLUENCE OF WINDS ON DIFFUSION. 
81 
FECUNDITY OF OVIPAROUS FORMS. 
The oviparous forms are far less prolific than the viviparous. They 
produce, under favorable circumstances, from 1 to 10 eggs, or an 
average of 5.4 eggs per individual. This average was made up from 
observations on 27 individuals. 
ABERRANT INDIVIDUALS. 
During our studies of Toxoptera we have found some rather inter- 
esting abnormalities. In December, 1907, 1 while dissecting some 
individuals in the laboratory, two were found that contained both 
living embryos and true eggs. In April, 1908, Mr. C. N. Ainslie found 
the same phenomenon occurring in 
individuals here in Washington. 
These latter resembled the wingless 
viviparous forms externally (see fig. 
16). Mr. S. J. Hunter, in " The 
Green Bug and Its Enemies," finds, 
besides this form, what he terms 
"winged intermediate females, re- 
sembling the winged agamic females 
in antennal characteristics." Other 
writers mention the same phenom- 
enon as occurring among other species 
of plant-lice, and no doubt these abnor- 
malities occur much of tener than any 
of us are aware. At present, however, 
there appears to be no satisfactory 
explanation of such occurrences. 
One single instance came under our observation where a puparium 
produced 6 young and then died. The cauda of this individual 
resembled that of an adult insect and the wing-pads were aborted, 
the abdomen being much broader than that of the normal pupa. 
(See fig. 17.) 
INFLUENCE OF WINDS ON DIFFUSION. 
By referring to the maps (fig. 5) showing the area covered by the 
different outbreaks of Toxoptera in the United States, west of the 
Mississippi River, it will be observed that they have all had their 
origin in central Texas, with a single exception, extending broadly to 
the north and northeast. This was especially true of two most des- 
tructive invasions of 1890 and 1907, and was also implied by that of 
1901, the case of 1903 having been too incipient. This strongly indicates 
Fig. 17.— The spring grain-aphis: Aberrant 
female pupa which produced young. En- 
larged. (Original.) 
1 Proc. Ent. Soc. Wash., vol. 10, pp. 11-13, January. 
26675°— Bull. 110—12 6 
