aote 
Undercooling and freezing points.--L. C, Fife and W. L. Owen,. 
Presidio, determined the undercooling and freezing points of Ex- 
eristes larvae to be 3.40 + 0.7° F. and 16,3° F., and for hibetnat- 
ing pink bollworm larvae 12.5 + 1° F, and 26° F., respectively. 
The larvae of both species survived after the formation of ice 
crystals within the tissues or when subjected to the undercooling 
point but once. This confirms the results of the tests with the - 
pink bollworm made by F. A. Fenton and A, C, Johnson several years 
ago when they reported that air temperatures as low as 11° F, must 
be reached and maintained for at least 34 hours before any appre— 
ciable kill will result. These studies, showing that the parasite 
Exeristes roborator will survive lower temperatures than the pink 
bollworm, are not surprising, as this parasite has been established 
on the European corn borer in the Northern States, whereas the pink 
bollworm has never become established in a region with low winter 
temperatures, 
Field population and mortality of pink bollworm.--D. L. Isler, 
W. L. Owen, and others of the Presidio, Tex., laboratory examined 
87 samples from 14 cotton fields in the Big Bend district last Noven— 
ber and December to determine the number and distribution of over-— 
wintering pink bollworms present in the fields after the cotton had 
been picked. Each sample consisted of 1 square yard of soil to a 
depth of 2 inches with all surface trash and the plants found within 
the area sampled. The nunber‘of pink bollworms for the different 
fields examined ranged from 3 to 52.2 with an average of 18.37 worms 
per square yard for the district. Of this district average, there 
were 2.54 worms per square yard, or 13.83 percent, in the soil, and 
the remaining 86.17 percent in the surface trash and in forms on 
the plants. In 1932 at approximately the same dates these same 
fields averaged 14, 53 worms per square yard, with only 7.71 percent 
of them in the soil. The percentage of larvae in the soil which can- 
not be destroyed by field clean-up was approximately twice as great 
in 1933 as in 1932. In some fields the increase in population was 
because the floods of 1932 had killed many of the worms. 
As all of the cotton plants together with most of the infested 
forms on the plants and soil surface in the Big Bend district have 
been burned during the last 2 years, the picture of the pink boll- 
worm Carry-over has completely changed and the worms in the soil 
are of greater importance, Experiments are under way at Presidio 
and Tlahualilo to determine the survival of the worms in the soil 
with different cultural treatments and in comparison with survival 
in bolls. The natural mortality is high and 94.24 percent of the 
live worms in the soil in unplowed and unirrigated plats at Presidio 
were dead by March 21, 1934, whereas over 97 percent were dead by 
this date in plats plowed and irrigated on January 8. The incon 
plete results indicate that the same cultural practices of plowing 
and irrigating early in the winter which increase the mortality of 
worms in the bolls will also be effective for larvae in the soil. 
