590 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
semiglobose, moderately large, but narrower than the thorax, pale 
brown, or concolorous with the body, the body cylindrical, enlarged 
at the thorax, and never with distinct bright marks. The thoracic legs 
are vestigial and fleshy and the prolegs are wanting. Lateral lobes 
are prominent. The ultimate segment has a distinct suranal process 
and the sternum has a pair of inconspicuous subanal appendages. The 
larvae are internal feeders and transform to the pupal and adult 
stages in their tunnels. 
The full-grown larva of the willow shoot sawfly (Janus abbrevia- 
tus (Say)), is about 14 inch in length (fig. 173). It is white and 
cylindrical, with fleshy thoracic legs which are not distinctly jointed, 
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Ficure 173.—The willow shoot sawfly (Janus abbreviatus). 
and no abdominal prolegs except a small pair on the underside of the 
last segment. The tip of the abdomen is furnished with a short, tubu- 
lar prong. This species attacks poplar and willow, in the North- 
astern States, westward into Minnesota, and southward into Texas, 
The adults emerge late in May and in June, and the females puncture 
the shoots of willow and poplar in which they deposit their eggs 
They often weaken or girdle the shoots above the point of egg laying 
The larvae, however, cause the principal injury by boring down the 
shoots through the pith (fig. 174), killing back the shoots for varying 
distances.: The larvae become full grown late in the summer and 
make cocoonlike structures by lining the occupied portion of the bur- 
rows with thin, glazed, transparent membranes. The winter is passed 
