14 
CARROT. 
with genial showers, the plant will rally from the attack of the 
numerous parasites.* 
“ My first impression was to plough up the plot of about two acres. 
My salesman advised patience, and to hoe the piece again. After an 
interval of ten days the improvement is not marked. 
“ Do we trace these and similar epidemics to the long prevalence 
of east wind in the spring ? The growth of the plants is checked, 
and the insects apparently redouble their efforts, and stifle the crop in 
its infancy.” 
This remark of Mr. Glenny’s is well worth attention, for it gives, 
as a practical and field observation, the important point of checked 
sap acting in hastening Aphis-development, which Mr. G. Buckton 
drew attention to scientifically and experimentally some years ago. 
I give the passages at length :— 
“ The addition of wings to the viviparous females obviously must 
much facilitate the spread of each species. This modification of form 
does not occur at fixed or stated intervals, hut appears to be in some 
measure induced by an overcrowded state of the colony, and with a 
deficiency of food. Gardeners are well aware of the sickly and 
poisoned conditions produced in those plants which are subjected to 
the exhausting and irritating attacks of Aphides. When the nutritive 
juices of the infested plants begin to fail a change commences in the 
larvae of those Aphides which are subsequently born. Swellings occur 
on the sides of the meso- and meta-thorax, within which the wings of 
the future imago are developed. I have repeatedly observed 
the effect of stinted food in hastening the development of wings, whilst 
keeping the larvae in confinement under bell-glasses. 
“ Some naturalists have thought that the often sudden appearance 
of swarms of winged Aphides in early spring may be caused by the 
action of the nipping easterly winds, which, by checking the flow of 
sap in the vegetation, remotely produces the same effect on the insects 
as the stinted food above noticed. To this atmospheric condition, 
which is usually accompanied by insect swarms and a peculiar haze, 
the popular voice gives the name of blight. Similar conditions of 
food and climate probably operate to produce the second large 
migratory flights of early autumn.”! 
The above views, which seem to me very much borne out by what 
we constantly observe, namely, that the checked growth caused by 
bad attack of Aphides is favourable to their rapid increase, points 
to the special benefit of washes which may kill the Aphis as fly 
or louse on the leafage, and likewise, by falling round the plants, may 
* “Lettuces are also suffering from the same enemies, and they are difficult to 
clean, and consequently unsaleable.” 
f ‘Brit. Aphides,’ by G. B. Buckton, F.B.S., vol. i., pp. 72, 73. 
