July i, 1921 
Larval Stages of H. bovis and H. lineatum 
443 
species. The wide spaces of the diagrams represent the ventral surface 
(on the left) and the dorsal surface (on the right) and the narrow spaces 
the three rows or lateral divisions. The present diagrams were enlarged 
by the addition of the three narrow spaces on the right in order to show 
both lateral surfaces and indicate the variations of the spiny armature 
so often found on the lateral divisions of the same specimen. The 
spines on the anterior and posterior borders are represented in size and 
approximate number as they appeared on the specimens selected for 
study. On the anterior border the heavier spines curve backward, 
and on the posterior border the numerous smaller spines curve forward. 
By referring to the tables it will be seen that the variations in distri¬ 
bution of spines are more marked on the posterior borders of the seg- 
• Dorsal 
Lateral 
Ventral 
Lateral 
Dorsal Lateral 
I 
1 
r*7 
imi.mmmmjh i.v.v'u 
"TV 
1 ^ 
0 
*?-?> 
so* 
z 
\~y 
U'. 
sgg) 
s ■& 
1777? 
\"vM" MVW fw 
WA» 
* \ 
•Mtr 
> * 
Wt 
0 
'*W»' ''tW'W 
w 
tvsr 
wr 
9 V','. 
tiOtl. 
0 
r '4 K \S v‘'*< 
Mb 
Mi 
1W W *1* ’JJV 
w 
*f%W' 
\\vw' 
4'Sf 
* 
ids* 
mi* h ^ *t% 
^Vf!’ 
tZ$ 
KJLH* 
4 
m. 
fll®. 
,. ;>i 
& 
■£&> 
vv«r 1 
’Wtv 
e 
•I'V* 
•W 
» >V "»\'4 
Uhl 
jcMIte 
t 
O 
<S& 
/m 
vSfii 
’Ml 
•H<W 
W 
6 
• *\\VS'^ WW ”'5 V* 
U*VT? 
v.v.f 
•fix Ml* 
»*|Vf 
•"*V 
1 ? 
m 
Itfv* l '7V" -M* ’"JS 
r? 
•w wW 
Wr 
-Ml 
VVf 
1 
«!»• 
7 
ms 
HSflfc 
rttXt 
ssi ; te 
w tmwfno 
A 
•s*v«i«v»vfjvw 
'VI,' 
Mrn 
Mf*’ 
O 
vVUf. 
.Vl.'/M 
MW 
’9 
1 
1 
i 
1 
jJSVV.V. 
10 
. 1.1 
Fig. 3—Hypodenna bovis: Arrangement of spines Fig. 4 .—Hypoderma bovis: Arrangement of spines on 
on the segments of a fifth-stage larva with a the segments of a fifth-stage larva with a heavy 
light coat of armature. coat of armature. 
ments except on the ventral surface. On this surface the occurrence 
of spines is almost constant—tliat is, all segments from 2 to io are 
armed on their posterior borders in H. lineatum and all segments from 
2 to 9 are so provided in H. bovis. The spines occur on the anterior 
borders of segments 2 to 9 in both species, only one exception being 
noted in H. lineatum , in which segment 9 was unarmed on this border, 
and in H. bovis one instance in which segment 10 was armed anteriorly, 
in addition to segments 2 to 9, inclusive. On the lateral divisions of 
the segments and on the dorsal surface the variation in occurrence of 
spines is much more marked. It is not uncommon to find certain seg¬ 
ments unarmed dorsally while on either side spines are found. The 
number of larvae showing such variations is indicated by letters in the 
figure columns which refer to footnotes. 
