PROGRESS REPORT ON THE EUROPEAN CORN BORER 95 
That the percentage of larval establishment and survival in the 
field is higher than that obtained in the experiment previously 
described is indicated by an analysis of 236 isolated infestations 
found in Ohio cornfields during 1924, wherein an average of 1.88 
larvae were collected per infestation. Since each of 731 egg clusters 
collected in the field earlier in the season contained 15.5 eggs, on an 
average, the survival of 1.88 borers per infestation shows that 12.13 
per cent of the eggs involved developed into larvae which became 
established, assuming that each of these isolated infestations devel- 
oped from a single egg cluster. 
VOLUME OF PLANT TISSUE CONSUMED OR REMOVED BY LARVAE 
The tunnels of 41 fully grown larvae which had spent practically 
their entire feeding period in isolated sweet corn and dent field 
cornstalks, were measured and found to average 8.6 inches in length. 
(See Table 14.) The tunnels of 35 of these larvae in sweet corn 
were found to average 0.2492 cubic inches in volume, and the tunnels 
of the 6 larvae in dent field corn averaged 0.1690 cubic inches in 
volume. It was not possible to determine the relative proportion of 
plant tissue which had actually been consumed by the larvae in 
comparison with the proportion of the tissue which had been bored 
out and cast aside during the excavation of the tunnel. 
DISTRIBUTION OF LARVAE IN THE PLANT 
While the host plant is green and succulent, it may be entered and 
tunneled by the feeding larvae at practically any point, but as the 
plant nears maturity and begins to dry out in its upper portions, or 
breaks over as a result of larval injury, the larvae exhibit a tendency 
to migrate to the lower and more succulent portions. 
On September 27, 1921, 78 per cent of the stalks were found to be 
infested in a 4-acre field of flint field corn at Stoneham, Mass., aver- 
aging 5.3 larvae per infested stalk. A total of 65.4 per cent of the 
larvae were distributed in the lower third of the infested stalks and 
the remaining 34.6 per cent in the upper two-thirds of the stalks. 
In this same field and on this same date a record was made of the 
relative distribution of the larvae in the stalks, ears, and ear stems 
of 10 plants showing average infestation. In these 10 plants 63.3 
per cent of the larvae were distributed in the stalks, 23.3 per cent 
in the ears, and 13.3 per cent in the ear stems. An analysis of the 
larval distribution in partly matured plants of dent, flint, and sweet 
corn which were dissected at Sandusky, Ohio, during the period from 
August 12 to September 1, 1924, showed that in a total of 474 larvae 
involved in these dissections 17.29 per cent were distributed in the 
lower quarter of the stalks, 18.77 per cent in the lower middle quarter 
of the stalks, 16.66 per cent in the upper middle quarter, 16.45 per 
cent in the upper quarter, 10.97 per cent in the tassel, and 19.82 per 
cent in the ears. 
The relative distribution of the larvae in the stalks and stubble 
is subject to considerable variation in accordance with the height of 
the stubble left after cutting, the date stalks were cut, and the stage 
of development of the plant when cut. There is also a certain 
amount of larval migration to stubble from corn which is cut and 
