116 THE CANADIAN ENTOMOLOGIST. 



The tracheal system is comparatively simple, consisting of two 

 longitudinal trunks sending off laterals in each abdominal segment and 

 one stout branch to each leg. Anterior branches supply the brain 

 and the eyes. 



Second Instar. 



A marked increase in size is noticeable^ the length being now 

 about 1.9 mm. and the width about .9, roughly one-half as much. 

 Head strongly convex, the frontal margin with a row of rather long 

 bristles, longest in the middle, shorter toward the eyes. Posterior 

 border deeply sinuate or arcuate. 



Prothorax about as long as mesothorax, the two together a trifle 

 longer than metathorax ; the contour of the two together forming a 

 narrow oval. Posterior margin of metathorax straight, anterior 

 margin concave ; its median length about equal to that of head. 

 Abdomen truncate, seven-jointed, last joint about ^ as wide as first 

 joint, terminated by two groups of rather long setae at the angles. 



Tarsi all one-jointed. First tarsus fringed with moderately long 

 setœ, about equal to tibia in length. Second legs ; tarsus equal to 

 tibia, both together about as long as femur. Third legs with femora 

 but slightly flattened, tarsus nearly as long as femur and tibia 

 together, clothed with setae, these longest at the joint, becoming 

 much shorter distally. Colour very transparent. A median grayish 

 line on thorax. 



Third Instar. (Fig. 3.) 



Length 2 mm. Width i mm. Head as before. Eyes a little 

 more than 1/5 the head-width in width. The wing-pads first appear ; 

 about 3/5 the length of thorax, sparsely hairy. Thorax y^ as long 

 as wide. Abdomen as before, fringed on the sides by rather long 

 setae, the posterior angles with conspicuous tufts. Ventral surface 

 sparsely pilose. 



Tarsi all one-jointed. The whole first leg about equal in length 

 to the femur of second leg. Tarsus about three times as long as 

 broad, terminated by a sharp spine. Second legs slender ; tarsal 

 claws as long as tarsus, other joints as in third leg, all feebly setose. 

 Third legs; tarsus i^ times the tibia, the latter equal to femur. 

 Tibia and femur together about equal to femur of second leg. 

 Abdomen strongly truncate. 



Fourth Instar. 

 Length 3 mm. Width 1.2 mm. Very much more pigmented 

 and less transparent than previous inrtars. Posterior margin of 



