PROGRESS REPORT ON" THE EUROPEAN CORN" BORER 151 
especially important during 1926, when the nocturnal temperatures 
and the direction of the prevailing wind during critical periods were 
both very favorable for the flight of large numbers of the moths. 
PARASITES 
NATIVE 
Native parasites have not exhibited any tendency to increase their 
effectiveness as natural enemies of the corn borer. The egg-parasite 
Trichogramma minutum Riley continues periodically to parasitize 
considerable numbers of the eggs, but its effectiveness is confined 
usually to the second-generation eggs in New England every second 
or third year. A few additional species parasitic on the larvae and 
pupae of the corn borer have been recorded, but their combined 
parasitism usually has affected less than 1 per cent of the total 
number of hosts collected or observed each year. 
FOREIGN 
Including the month of October, 1926, a total of about 225,000 
foreign parasites have been liberated in nine different locations of the 
corn-borer infested areas of Michigan, Indiana, Ohio, Pennsylvania, 
and New York. Seven distinct species were involved in these libera- 
tions, viz: Exeristes roborator Fab., Microgaster tibialis Nees, 
Habrobracon brevicornis Wesm., Eulimneria crassifemur Thorn., 
Apanteles sp., Angitia punctoria Roman, and Phaeogenes planifrons 
Wesm. Recoveries of E. x roborator were made in New York during 
1924, 1925, and 1926. This species was recovered in Ohio during 
1925 and 1926. A very recent recovery of what may prove to be 
M. tibialis was made in Ohio. Special precautions, of course, were 
taken to prevent the escape of foreign hyperparasites. 
Similar introduction work in New England has resulted in the 
liberation of about 1,187,000 foreign parasites in infested cornfields 
of that section. Ten different parasitic species were involved, con- 
sisting of the seven species listed in the preceding paragraph and 
in addition Macrocentrus sp., Zenillia roseanae B. B. and Masicera 
senilis Rond. Five species of these foreign parasites have been 
recovered in New England under circumstances indicating their 
permanent establishment, viz : E. roborator, M. tibialis, E. crassi- 
femur, A. punctoria, and P. planifrons. In certain fields the col- 
lections have demonstrated that the prevailing total parasitism by 
the foreign species exceeds that of the native species. The rate of 
importation of foreign parasites from Europe has been increased 
and preliminary shipments have been received from India. It is 
expected that this work will be greatly stressed in the near future. 
CONTROL 
None of the types, varieties, or strains of corn thus far tested has 
shown any practical immunity to corn-borer attack except when 
involved with time of planting such varieties. 
Those varieties of corn characterized by large stalks and ears 
have continued to exhibit a greater resistance to severe injury by 
the corn borer than the varieties which possess smaller stalks and 
ears. 
