334 E. H. STRICKLAND. 



EXPLANATION OF PLATE III. 



FIG. 8a. Average size full-grown parasitized larva of Simulium hirtipes meas- 

 uring II mm. 



FIG. 8b. Average size mature larva of Simulium hirtipes, measuring 8.5 mm. 

 showing darkened pupal histbblast, a. 



FIG. ii. Median sagittal section of a half-grown healthy larva to show the 

 alimentary tract, b, the normal position of the spinning glands, which extend 

 backwards from the pharynx on either side latero-ventrally to the alimentary 

 canal, doubling back on themselves at about the point b,' where one has been cut 

 in cross section; c, the normal quantity of fat body which increases still more as 

 maturity approaches; d, one of the pharyngeal glands. (This is not seen in an 

 exact median section, as the two glands are narrowly separated medially.) 



