February, ’24] 
JONES: CORN BORER PARASITES 
119 
are having some success in breeding this species, and hope to liberate a 
worthwhile number in 1924. 
Habrobracon brevicornis Wesm. is a small hymenopteron upon which 
most of our efforts were expended in 1922. This species attacks full 
grown larvae, paralizes them, and deposits external eggs. Resulting 
larvae feed externally and produce an average of some 18 small white 
cocoons per host. Eight or even ten generations per year would be pos¬ 
sible, as the life cycle is short, and varies greatly with the temperature. 
Hibernation is in the adult stage. In September 1921, 1210 cocoons 
were received, from which 715 male and 213 female adults issued. 
Four hundred adults were liberated later in 1921, and 1,054,000 in 1922. 
I consider it important to add that in 1921, liberations averaged 14% 
females, whereas our 1922 liberations averaged approximately 40% 
females. 
Exeristes roborator Fabr. one of the old Pimpla group, is a large 
hymenopteron with a long powerful ovipositor and is able to locate and 
parasitize full grown larvae through corn stalks and even burdock 
stalks. The host is killed, and eggs and larvae are external. It has 
several generations a year, and hibernates as a full fed larva in a very 
thin tough cocoon. In October 1922, 1,061 cocoons arrived which 
produced about 500 adults of which number 56 were liberated, and the 
remainder were used in breeding experiments. In 1923, 28,935 adults 
were bred and liberated. Females predominated and through the use 
of a special emergence cage, were well mated before liberation. 
Microgaster tibialis Nees., a small hymenopteron, shows up well in 
northern France, especially in the weed areas. It parasitizes second 
instar larvae and kills the host in the late fourth or early fifth instar 
and hibernates within very tough white cocoons. Although it has 
not been liberated in this country, we have solved most of its breed¬ 
ing problems through an importation of 100 cocoons in 1923, and expect 
to breed it for liberation in 1924. 
These species mentioned, comprise those of importance found in 
France and Italy, but information received leads us to hope that other 
valuable additions may be had from Hungary and Japan. 
No systematic collections for recovery of liberated parasites have been 
attempted, except in the case of Habrobracon brevicornis Wesm. and no 
recoveries of this species were made. However, Exeristes roborator has 
shown up extremely well in incidental collections with as high as 8% 
near colony sites, commonly 1 to 4% in a corn field mile from the 
