June, ’20] 
AINSLEE: CORNPITH WEEVIL 
273 
mm. in size, its margins often a little ragged and at first concolorous 
with the surrounding stem but soon darkening for a short distance 
back from the puncture. The number of punctures varies according 
to the abundance of the beetles and the length of time the stem has 
been exposed. Counts at several times and places have given the 
number from one to eleven per plant, the average 
between four and six. Not all of these are egg 
punctures as many seem to be made for feeding 
purposes only. Externally the two are indis¬ 
tinguishable. I have never seen the punctures 
elsewhere than on the upper part of the stem 
and in the tassel but Mr. E. H. Gibson reports 
that in Mississippi the beetles commonly feed on 
the midribs of the leaves where the tissue is of 
much the same character as in the stem. 
In making the puncture the beetle stands trans¬ 
versely on the stem and after cutting through 
the bark consumes enough of the pith to form 
a small cavity which always lies to the side 
of the opening, never above or below it, in¬ 
dicating that the beetle does not rotate while 
feeding as do many rhyncophora. The operation requires from thirty 
minutes to an hour to complete and if it be a female preparing for an 
egg she then steps forward, presses the tip of the abdomen to the punc¬ 
ture and inserts the egg. When in situ the egg lies in the pith a milli¬ 
meter or more from the outside surface and usually distorted from the 
unequal pressure. The egg is so soft that its shape is never twice alike. 
It resembles nothing so much as a bit of water-clear jelly. When 
freed from pressure it is oval or elliptical in outline, sometimes a little 
flattened or slightly reniform, or almost cylindrical, .670 to .699 mm. 
long and 0.40 to 0.42 mm. broad, considerably larger than the puncture 
through which it enters. The chorion is very tenuous and without 
markings save for small accidental wrinkles. 
As development proceeds the egg becomes milky and a day or two 
before hatching the brown mandibles can be seen through the chorion. 
One egg whose deposit was observed on July 22 had not hatched when 
dissected from the stalk on July 29 but the mandibles were plainly 
visible so the egg stage is probably but little over a week. After the 
nidus is once opened it is difficult to keep the egg from drying or molding 
for more than a day or two. 
The hatching is nothing more than a rupture of the delicate mem¬ 
brane inaugurated and assisted by the mandibles which can sometimes 
be seen slowly opening and closing before the membrane breaks. The 
Fig. 9.— a, Section of 
corn stalk just below 
tassel, showing egg 
punctures; b, Section 
with sheath removed to 
show exit hole of larva. 
