83 
The wheel bug (Prlonidus cristatus) was observed attacking the 
nymphs of this bug on several occasions during June. 
The Cabbage Looper (Plusla brasslcse Riley). — The observations which 
were conducted on this species were much the same as for Pieris 
rapm, with which it was associated. Numerous larvae were still living 
in the fields as late as the middle of December. At this time one larva 
was found less than half grown, showing that the eggs had been 
deposited about the last week of November. 
The Cabbage Plant-louse (Aphis brasslcse Linn.). — Of this species it 
was observed that numerous individuals, but no winged forms, wer , 
still present in cabbage fields by the middle of December, mostly, 
however, in the hearts of cabbage where they had crawled for protec- 
tion. No parasites or other enemies could be observed at this time. 
A number of individuals of this plant-louse were kept in the insectary 
of this Department in the coolest temperature that could be obtained, 
the object being to have them furnish food for ladybirds. It was 
noticed that they survived a temperature of 20° F., which occurred 
during three successive days in February, and that they were active a 
few degrees above the freezing point, seeming to be able to fly, since 
winged individuals were found at the top of rearing cages a foot 
above the plant on which they had been feeding at a temperature a 
little below 40° F. Meanwhile the ladybirds, although not dormant, 
were inactive, responding feebly to stimulation. 
CONCLUSIONS. 
The practice of planting late cabbage and other crucifers is calcu- 
lated to be of great benefit to several species of insects, particularly 
those just mentioned, and the particular reasons are that, as a rule, 
natural enemies, such as parasites and wasps, and diseases are less 
active in cool weather, while their hosts are seemingly nearly as active 
as in warm weather. This, of course, is not really the case; they do 
not work so many hours in a day, and their growth is slower. The 
trouble is that the farmer and truck grower generally, at least in those 
parts of Maryland and Virginia lying near the District of Columbia, 
appear to think that the insects have disappeared to such an extent 
that it is not necessary to apply remedies. For the imported cabbage 
worm, the looper, and the larva of the diamond-back moth, this is the 
best time to make applications of poisons, as the crops are not needed 
until a considerable time after poisons are applied, and this does away 
with any danger of poisoning to human beings. Many individuals of 
the insects mentioned, without doubt, perish for lack of food, as most 
wild crucifers are dead at such times. 
Such cabbage as is pulled and "heeled in" and covered with under- 
brush is apt to carry with it many individuals of all of the five cabbage 
pests under discussion, and when the cabbage heads are covered with 
