February, ’18] 
PADDOCK: TEXAS APHID NOTES 
31 
Of the species of aphids carefully investigated to date, the normal 
form of reproduction is asexual throughout the entire year. This 
has been found to be the case in the green bug, the turnip louse, and 
the melon louse. Even as far north in the state as Witchita Falls, 
close to the 34th parallel, viviparous development of aphids persists 
throughout the winter. Here an inch of snow is not uncommon, which 
may sometimes remain on the ground for four or five days. Tem¬ 
peratures of 15 to 20° F. are not rare and there may be periods of a 
week when the temperature is not over 32° F. Under these condi¬ 
tions, the turnip louse and the green bug survive, and reproduction is 
only retarded. In the extreme southern section of the state where 
freezing temperatures are uncommon, asexual reproduction proceeds 
uninterrupted. In January at Brownsville the daily reproduction in 
the turnip louse was six to eight young, equal to ideal autumn condi¬ 
tions at College Station. At Brownsville, Vickery reared 107 succes¬ 
sive generations of the corn-leaf aphis. Only 35 successive generations 
of the turnip louse were reared at College Station but these occured in 
twelve months. Sixty-two successive generations of the melon louse 
have been reared at College Station in twelve months. In all of these 
cases, no sexual forms have appeared. 
In Texas, the summer conditions are more severe for the aphids to 
withstand, than are the winter conditions. During the very long, 
hot and dry summers, green succulent vegetation is found in only low, 
damp and protected places. With the green bug, the migration from 
grain occurs during June and July, which is the time of the ripening 
of the grain. During the summer, it was impossible to find any lice 
in the grain fields, and even if the growing grain was available at this 
time, it is doubtful if the green bug could survive the temperatures 
which prevail. It was with much difficulty that the turnip louse was 
reared throughout the summer on turnips when none were to be found 
in the field. The melon louse feeds entirely on cotton and okra during 
the summer months, these hosts being the only ones that are available 
at that time. 
In the turnip louse, with the approach of hot, dry weather, there is a 
decided reduction in the number produced daily, and all of the stages 
of life-history are lengthened much the same as under winter condi¬ 
tions. The same condition has been as pronounced in the melon 
louse in our cage rearing experiments. The month of August seems 
to be the most severe in the year for the aphids to withstand. During 
the summer months, general collection of aphids is almost impossible, 
the spring and fall months being the best for collecting purposes. 
In one case, we find a complete reversal of the life-history in the 
beet louse, Pemphigus betce Doan. The alate viviparous females of 
