NORTH AMERICAN SPECIES OF BRANCH INECTA. 253 



8, 9, 10, ii, 12; PL XL, 23, 24). Viewed from the front or back, 

 the tips of B. Lindahli are much more gradually pointed than 

 those of B. coloradcnsis (PI. X., 7, 9, 1 1), but when viewed from 

 above or below, the reverse is true. This is due to the fact that 

 the already flattened second division of B. Lindahli is still more 

 flattened on the outer or lower side as the inturned tip is ap- 

 proached, and this gives the lower part a truncate or slightly 

 convex appearance (PI. X., 7, 10, 1 1 ; PI. XL, 24). In B. colora- 

 dcnsis, instead of the lower part of the tips being flattened, there 

 is developed a prominent ridge and this, together with a less 

 prominent ridge on the upper side, gives the tip a very blunt ap- 

 pearance when viewed from the front (PI. X., 8, 12 ; PI. XL, 23). 

 The tip in B. coloradcnsis is flattened on the anterior and pos- 

 terior sides, while the tip in B. LindaJdi is flattened dorso- 

 ventrally. 



In B. pahidosa the second division of the clasper tapers rather 

 gradually to the blunt end, which is not inturned as in the other 

 two species under consideration. The ratio between the length 

 of the second joint and the first is for B. coloradcnsis, I to 1.68 ; 

 for B. Lindahli I to 1.36; and for B. pahidosa I to 1.28. 



In young specimens of B. coloradensis the tubercle of the basal 

 joint is often absent. It is also not uncommon to find such spec- 

 imens with the second division ending rather bluntly, and not 

 inturned. When in this condition, the second division resembles 

 the corresponding division of B. pahidosa. 



The eggs of B. pahidosa and B. Lindahli are of the same size 

 (Packard, 1883 : 340). Those of B. coloradensis are much larger, 

 the ratio being 1.74 to I. 



The average length of the ovisac of B. coloradcnsis was 6. 1 7 

 mm., varying from 4 mm. to 8 mm.; that of B. Lindahli was 

 3.71 mm., varying from 2 mm. to 5 mm., the ratio between the 

 two species being 1.66 to I. The ovisac of B. Lindahli is 

 thicker in proportion to its length, and often contains 50 or more 

 eggs arranged in from three to five rows, while the ovisac of B. 

 coloradcnsis seldom contains as many as 30 eggs, and these gen- 

 erally arranged in from one to three rows (PI. XL, 17, 18). 



The caudal appendages of B. Lindahli are much longer in pro- 

 portion to their breadth than those of B. coloradensis (PI. XL, 19, 



