THE IMPORTED CABBAGE WEBWOKM. 
31 
cultivated plants, such as "Japanese radish," are subject to attack 
and injury. Among weeds and wild food plants are the common 
shepherd's purse {Bursa [Capsella] bursa- past 'oris) and "pussley" 
or "cutter's grass," otherwise purslane (Portulaca oleracea), 
NATURAL ENEMIES. 
Natural enemies of cruciferous insect pests are of great value in 
keeping their hosts in check, and some dependence must be placed 
upon these agencies in restraining the undue multiplication of this 
webworm. Indeed, there is evidence that they do hold it in check 
in many regions, al- 
though they have not 
prevented its natural 
spread. 
In spite of the short 
time that we have 
known of its occur- 
rence in this country 
as a pest — since about 
1899 — we are already 
certain that at least 
five natural enemies, 
and probably more, 
are at work in deci- 
mating its numbers. 
Exorista pyste Walk, 
(fig. 6), a tachina fly, 
has been repeatedly 
reared from the cater- 
pillar of Hellula undalis from July 27 to as late as October 27. 
Limnerium tibiator Cress., a very abundant parasite reared with 
this species, is an ichneumonid. It was reared from the latter part 
of October until the last week of December. It has not been posi- 
tively ascertained to prey upon this larva, as it is a well-known enemy 
of the diamond-backed moth (Plutella cruciferarum Curt.), which 
was also present in smaller numbers, but as it is also known to attack 
the cabbage looper (Autographa brassicm Eiley) and Mineola indi- 
ginella, it seems probable that it is in reality an enemy of this web- 
worm. 
Plagiprospherysa sp., a tachinid fly parasite, was reared June 12 
an<j 17, 1908. from its host from Brownsville, Tex. The identifica- 
tion was made by Mr. C. H. T. Townsend. 
Two other hymenopterous parasites of this webworm, reared in 
1899, were identified by the late Dr. William H. Ashmead as Meteorus 
vulgaris Cress, and Temelucha (Porizon) macer Cress., female. The 
Fig. 6.- 
Exorista pyste, a parasite of the imported cabbage 
webworm (after Titus). 
