452 
Journal of Agricultural Research 
Vol. XXI, No. 7 
consisting of at least five rows, in all of which the spines are slightly 
larger and more uniform, in size throughout than on the preceding 
segments. Laterally this band of spines narrows down to the first two 
or three rows which extend on around over the dorsal side. The eleventh 
or caudal segment is armed with spines of three distinct types. Along 
the anterior border are a few small spines similar in structure to those 
along the anterior border of all the preceding segments. Closely following 
these, except for a narrow space ventrally, are numerous stout spines 
consisting, of a large, circular, blackish, slightly elevated base, in the 
interior of which arises a short, stout spine less in length than the diameter 
Fig. 15. —Hypoderma lineatum: Cephalo- Fig. 17. —Hypoderma lineatum: Ventral view of second- 
pharyngeal skeleton and mouth hooks stage larva. X 13. 
of third-stage larva. A spine; B, ante¬ 
rior end, and D, posterior end, of mouth 
hooks; C, tooth. Greatly enlarged. 
of the base. Surrounded by these spines are the posterior spiracles, which 
are represented by circular spots or disks with two or three very flattened 
and triangular-shaped spines on the border of each. These flattened 
spines are hardly visible in the third-stage larva even under high magni¬ 
fication and disappear entirely with the fourth and fifth stages. The 
fused anterior terminal segments bearing the anterior spiracles, centrally 
located from an anterior view, and with the mouth hooks ventrally and 
the small hom-like appendage dorsally located, are thickly covered with 
a band of spines below the mouthparts, extending on around and beyond 
the spiracles laterally in a decreasing number toward the dorsum, where 
