SOME LEPIDOPTEROUS LARVAE RESEMBLING THE 
EUROPEAN CORN BORER 1 
By William 0. Ellis 2 
Assistant Entomologist , Cereal and Forage Insect Investigations , Bureau of 
Entomology, United States Department of Agriculture 
INTRODUCTION 
The European corn borer (Pyrausta 
nubilalis Hiibner) is unquestionably 
the most important potential insect 
enemy of the corn plant in the United 
States and Canada. Inasmuch as 
there are other lepidopterous larvae 
attacking corn which may be readily 
confused with the European corn 
borer, it seems desirable to give an 
account of these larvae, to point out 
the structural characters wherein they 
differ from one another, and briefly to 
discuss their habits and seasonal his¬ 
tories in order further to facilitate 
the identification of the European corn 
borer in the field, as has been done by 
Heinrich (13) z for the pink bollworm 
and lepidopterous larvae likely to be 
confused with it. 
The larvae of two native species, 
Pyrausta ainsliei Heinrich and P. 
penitalis Grote, which also inhabit corn 
at certain seasons of the year, so closely 
resemble the larvae of "Pyrausta nubi¬ 
lalis in color, size, and structure that 
their identification without final resort 
to the microscope will always remain 
uncertain. Immature larval stages of 
these three forms are especially difficult 
to separate. Other plants than corn 
attacked by the European corn borer 
are hosts of lepidopterous borers and 
surface feeders, some of which, although 
entirely unrelated to one another, 
resemble more or less closely the larvae 
of P. nubilalis. In order to draw a 
line, however, as to the forms to be 
included in this category, special con¬ 
sideration is given only to those larvae 
inhabiting the preferred food plants of 
the European corn borer. Field ob¬ 
servations in connection with the 
species discussed were conducted in 
the Massachusetts area infested by the 
corn borer, unless otherwise indicated. 
It was necessary in this work to 
make distinctions between food plants 
and shelter plants, as Ainslie and 
Cartwright ( 1 , p. 837) also found 
necessary in their work on the biology 
of Pyrausta ainsliei in Tennessee. 
Generally, the naming of a particular 
plant as a host plant implies that the 
insect feeds upon it and derives its 
livelihood therefrom. This is not 
strictly true, however, for some lepi¬ 
dopterous larvae boring in weeds and 
other plants migrate at certain seasons 
of the year, particularly in the autumn, 
to other apparently more suitable 
plants in which they find desirable 
quarters for the winter (2). Usually 
the larvae possessing this migratory 
habit—those observed—are full grown 
in the fall and consequently require no 
further food in the spring for the con¬ 
tinuance of their development. They 
have lived at the expense of small 
marrowed or pithy stems. When 
completely tunneled out, these stems 
are obviously frail and when subjected 
to the rigors of winter in the north are 
readily broken over, frequently expos¬ 
ing the burrows of the larvae within. 
Thus the larvae are feebly protected 
unless they migrate to more favorable 
situations or mine into the under¬ 
ground stems of the plants they infest, 
as do Gnorimoschema and Pterophorus 
in Solidago sempervirens L. Plants 
which afford only wintering or pupation 
quarters for an insect should be termed 
shelter plants. The term “ host plant ’’ 
is relative. 
Eleven species are considered in the 
present paper. Descriptive matter in 
the text has been reduced to a mini¬ 
mum; the important differentiating 
structural characters, however, are 
pointed out and further emphasized by 
figures. 
1 Received for publication Apr. 22, 1924; issued June, 1925. This study was projected by D. J. Caffrey, 
in charge of the European corn borer investigations, as an aid for field men. The writer materially bene¬ 
fited from his enthusiasm, suggestive criticisms, and general supervision of the work, and desires hereby 
to express his appreciation and thanks. It should also be stated that Carl Heinrich, of the Bureau of En¬ 
tomology, read the manuscript, pointed out omissions, and suggested several important changes both in 
the text and in the figures. 
2 Resigned Jan. 12, 1925. 
3 Reference is made by number (italic) to “Literature cited,” p. 792. 
Journal of Agricultural Research, 
Washington, D. C. 
( 777 ) 
Vol. XXX, No. 8. 
Apr. 15, 1925 
Key No. K-134 
