274 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 13 
membrane once ruptured and pushed aside, the head slowly changes 
to brownish yellow and the minute grub begins to feed on the delicate 
pith cells surrounding it. It turns at once downward and cuts a 
straight passage so small at first as hardly to be visible. The exact 
number of instars has not been accurately worked out. It would seem 
that this could be determined from the head casts left in the burrow 
and occasionally one of these can be found but after the first or second 
instar the larva becomes more active and instead of continuing directly 
downward it constantly moves up and down in the burrow enlarging 
it and crushing any exuvise into hopeless bits. I have made head 
measurements of a large number of alcoholic larvse but the sizes grade 
imperceptibly into one another, making any separation on this basis 
impossible. 
When the larva reaches the first node it pauses for some time either 
because the septum is harder to cut through or because the tissue just 
at the node is more succulent and attractive. In either case the node 
seems to be a favorite resting place and quite a cavity is cut out and 
partially filled with the fine, fluffy, pale yellow frass. When a stalk is 
opened the larva, in the majority of cases, will be found in or near this 
nodal cavity. Between the nodes the larva continues the burrow as a 
clean straight tunnel, a little wavy in direction but seldom with 
branches or side passages. Close to the egg puncture and also at the 
nodal cavities, the passage is somewhat discolored, yellow or brownish, 
elsewhere perfectly white and clean. The presence of the larvse is 
most easily determined by a smooth cut between the first and second 
nodes from the top when the passage, if present, appears as a clean 
round hole. I have thought that in some cases I could locate infested 
plants by external examination and it may be that the tassels and the 
upper nodes of infested plants become brown and dry a little sooner 
than the others but this method is not certain. . In no case have I 
observed from the work of this insect any breaking over of the tassels, 
but an instance of this was noted at Hagerstown, Md., September 29, 
1919, by Mr. C. M. Packard. Broken tops were found, many of them 
on infested plants, but as not all of the broken stems were infested it is 
hardly possible to attribute the condition to this insect alone. As 
these broken-over tassels are one of the most conspicuous evidences of 
the work of the European corn borer (Pyrausta nubilalis) further 
observations on this point are desirable. As each node is reached the 
'larva delays and enlarges a cavity there. Occasionally the larva com¬ 
pletes its growth at the top node, more commonly at the second and 
third and only very rarely does it reach the fourth node from the top. 
Although very often more than one egg is laid in a single plant it is 
very unusual for more than one of the larvse to reach maturity. All 
