Insect-Larva eating Rust on Wheat and Flax. 493 



the eyes, and a short third passing upward and inward and 

 articulating with a long slender piece of horn whose front 

 attachment is near that of the 

 jaw-muscles on the forehead. Fig. 2. 



This framework, by its 

 strength and elasticity, pre- 

 serves the form of the head 

 and serves at the same time 

 for the attachment of muscles 

 mostly retractive. Thus the 

 free ends of the hindmost 

 prongs serve for the attach- X20f) 



ment of at least three pairs Breast-bone or Anchor Process, 

 of muscles : — (1) fan-shaped 



muscles, passing downward and serving to lift the head ; (2) 

 narrow muscles, passing forward and serving to retract the 

 front portion of the head ; (3) narrow muscles, passing back- 

 ward and aiding to retract the whole head, an operation in 

 which they are assisted by muscles attached anteriorly to the 

 short prongs of the framework and posteriorly to the upper 

 part of the body- wall of the thorax. 



The most striking feature in the thorax is the peculiar 

 " breast-bone " (fig. 2) found -p. 



on the lower part. Seen from 

 the side this organ seems to be 

 of nearly uniform size through- 

 out and to be forked in front. 

 Seen from below, however, 

 it is found to be wider in front, 

 where it ends in a distinct and 

 somewhat heart-shaped head. 

 This breast-bone stiffens the 

 thorax, and very likely serves 

 other purposes. Fig. 1 also 

 shows the anterior thoracic 

 stoma ; the oval above and to 

 the right shows the relative size of a rust- spore (Puccinia 

 rubigo-vera) . 



Department of Agriculture, 

 Sydney, N. S. W. 



Note. — Since the above was written we have seen larvae on 

 plum-leaves feeding on the spores of Puccinia pruni, and 

 others on the rusted leaves of Bidens pilosus, which appear 

 upon careful microscopical examination to be identical with 

 those here described. 



Head, showing Mouth-parts. 

 (Dorsal and ventral views.) 



