50 
THE CABBAGE PLANT-LOUSE. 
(Aphis brassicw L.) 
This insect was quite troublesome this season from about the Ist of 
August to lst of September. After the latter date they could only be 
found in scattering colonies. During the worst period of attack they 
were so plentiful as to nearly ruin many plants. 
I mention them more for the purpose of speaking of the insects which 
preyed upon them than anything else. 
Of these the larve of the Syrphus flies (two species were reared) were 
the most persistent and literally swept the lice off by thousands. It 
was very interesting to watch these blind maggots in their work of de- 
‘struction. There were also present the larvae of Lady-birds and Lace- 
winged flies. These, however, did not do anything like the execution 
of the first-named insects. I noticed where lice were very numerous 
that a large per cent. became winged, while on other portions of the field 
it seemed that a much larger per cent. were apterous. 
CABBAGE WORMS. 
(Plusia brassice and Pieris rape.) 
August 3 a few larve of brassice were noticed in a patch of a 
couple of acres of Cabbage where rape were already quite abundant and 
doing considerable injury. They were so few that it was hardly thought 
possible they could do much harm the present year. On this date the 
rape as above stated were already numerous and doing much harm. 
A series of experiments was at once begun looking towards their de- 
struction. However, many of this brood pupated, and from the 10th to 
the 15th of August I never saw the rape butterfly so abundant as they 
were over the cabbage beds in the University garden. These deposited 
their eggs in great abundance, and after several days disappeared. 
Among the first brood of worms (rape) I had noticed a few larve af- 
fected by Apanteles glomeratus, and also several pup which had been 
stung by Pteromalus puparum. These did not appear to be abundant, 
but probably many were not noticed. As this second brood of rape 
developed it was hardly possible to find a larvee not affected by one of 
these parasites. A. glomeratus was most abundant, as it stings the 
young larve, but should one be so fortunate as to escape this insect, P. 
puparum was sure to find it. I noticed that the last named always 
stings the larva just before it makes the last molt or immediately after 
the pupa is formed. So well did these parasites do their work, that 
after the large brood of butterflies previously mentioned not an adult 
was seen except that now and then a straggling individual would sail 
over the field. In all of my experiments in boxes, during which I con- 
