442 
Journal of Agricultural Research 
Vol. XXI, No. 7 
“bump” of the newly encysted larva is so slight that it remains un¬ 
noticed even by a close observer, and later when more growth has 
taken place and the swelling has enlarged sufficiently to become plainly 
noticeable the larva is already well advanced in its next stage. 
DIFFERENTIATION OF H. EINEATUM AND H. BOVIS IN THE FIFTH 
INSTAR 
In the first, second, fourth, and fifth instars the larvae of both species 
bear a heavy, spiny armature in transverse rows, either broken or con¬ 
tinuous, across their body segments. Brauer found that by the presence 
or absence of armature on a certain posterior segment he could definitely 
identify the larvae of the fifth instar, heretofore called the fourth stage, 
by this character alone. In studying hundreds of specimens of both 
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Fig. i . — Hypoderma lineatum: Arrangement of Fig. a. — Hypoderma lineatum: Arrangement of 
spines on the segments of a fifth-stage larva with spines on the segments of a fifth-stage larva with 
a light coat of armature. a heavy coat of armature. 
species the writer found that this character always holds true and is 
therefore a good one. 
The arrangement and variation in the distribution of the spiny 
armature in fifth-instar larvae is clearly shown in figures i to 4 and 
Tables I and II. Figures r and 2 and figures 3 and 4 represent, respec¬ 
tively, the heavy and light armature of H. lineatum and H. bovis. The 
variations presented in Tables I and II are based upon a detailed study 
of the armature on 106 larvae of H. lineatum and 108 H. bovis. 
In the tables and diagrams Brauer (r) is followed in considering the 
first segments as cephalic and marked 1, as these segments are so closely 
fused and the sutures dividing them are often so indistinct that they 
appear as one. This method of diagraming the spines is a device adopted 
by Brauer to indicate the difference in spine distribution in the different 
