PROGRESS REPORT ON THE EUROPEAN CORN BORER 
135 
During 1921 a special effort was made to determine the seasonal 
variation in the parasitism by T. minutum and also to obtain a more 
correct average of the parasitism for the entire season than had 
previously been obtained in 1919 and 1920 when collections were 
made without proper regard to seasonal variation. The plan used 
in 1921 called for six uniform collections of eggs of Pyrausta 
nubilalis, three of each generation, in each of the 24 towns selected. 
In this manner an early, medium, and late collection of eggs was 
made from each town during the seasonal progress of each genera- 
tion, thus effectively covering all the seasonal variations that might 
occur in parasitism. As a result of this system the percentage of 
parasitism for 1921, as given in Table 44, is probably more nearly 
correct than the figures given for 1919 and 1920. These collec- 
tions also showed very plainly the seasonal variation in parasitism. 
Table 4A gives results of the six collections in four typical towns 
in Massachusetts during 1921. 
Table 44. — Seasonal variation in parasitism by Tricliogramma minutum in New 
England in 1921 
Town (Massachusetts) 
First generation, per cent 
of parasitism 
| ■ I 
Early Medium Late 
Second generation, per cent 
of parasitism 
Early 
Medium Late 
Wakefield 
Scituate.. 
Peabody. 
Danvers.. 



1.1 
0.5 
3.4 
5.5 
2.1 
4.3 
15.5 
11.9 
7 2 
78. 5 
90.5 
62.7 
13.6 
A small percentage of corn-borer larvae and pupae have been de- 
stroyed in New England each year by several different species of 
dipterous and hymenopterous parasites. The species which have 
been reared from Pyrausta nubilalis larvae and pupae are listed 
below : 
DIPTEROUS PARASITES 
Phorocera erecta Coq. 
Exorista pyste Walk. 
Masicera nu/oidea Desv. 
Exorista nigripalpis Towns. 
Carcelia ochracea V. D. W. 
Compsilura concmnata Meig 
HYMEXOPTEROI'S PARASITES 
Itoplectis conquisitor Say. 
»S a gar it is dubitatus Cress. 
Agrypon sp. 
Amblyteles brevicinctor Say. 
Amblyteles rubicundus Cress. 
Cryptus incertus Cress. 
Ephialtes aequalis Prov. 
Campoplex sp. 
Microbracon caulicola Gahan. 
The combined parasitism by the species listed above has totaled 
less than 1 per cent of the larvae and pupae collected each year. The 
parasitism of the first generation has been slightly greater than that 
of the second. A few individuals of the tachinid Exorista nigripalpis 
Towns, have been reared from P. nubilalis larvae collected in New 
Ilabrobracon gelechiae Ashin. 
Epiurus pterophori Ashm. 
Epiurus tecumseh Tier. 
Epiurus indagator Cress. 
Bassus agilis Cress. 
Labrorychus prismaticus Nort. 
Microgaster zonaria Say. 
Meteor us loxostegel Vier. 
