194 The University Science Bulletin. 



DESCRIPTION OF THE INSTARS. 



For the description of the variout^ instars an attempt was made to 

 select an average indivdual. It is possible to separate the males and 

 females of the same instar by an examination of the ventral surface 

 of the eighth and ninth abdominal segments. This is discussed later 

 in greater detail under the development of the genitalia of each sex. 

 Except for this, and a slight difference in size, the female being the 

 larger, the two sexes are practically the same. 



Egg. 



(Plate XVII, fig. 1.) 



Length, 1.25 mm. Greatest width, .41. Subovoid in shape, somewhat pointed 

 at one end; greenish yellow at first; just before hatching deeper yellow with 

 dark e3'espots. 



First Instar. 



(Plate XVI, fig. 1.) 



Length, 2.65 mm. Width across eyes, .65 mm. Pale yellowish white, eyes 

 black and prominent; anterior margin of head evenly rounded; two pairs of 

 wing pads present, first pair short, barely covering base of second pair, caudal 

 margin in form of an inverted W, with median projection extending farther 

 caudad than lateral projections, exposed portion of second pair more than 

 twice as long as first pair, caudal margin nearly straight, the segments marked 

 off by light brownish bands. 



Second Instar. 



(Plate XVI, fig. 2.) 



Length, 3.15 mm. Width across eyes, .9 mm. Color same as in first instar; 

 margin of head similar; wing pads have increased in length and width, but 

 relative shape and position are the same; caudal margin of second pair bent 

 slightly cephalad medially. 



Third Instar. 



(Plate XVI, fig. 3.) 



Length, 4.25 mm. Width across eyes, 1 mm. Color and shape of head un- 

 changed; wing pads show decided change in length and width, lateral angles of 

 first pair produced caudad and much longer than median projection; exposed 

 length of second pair but little longer than first pair. 



Fourth Instar. 



(Plate XVI, fig. 4.) 



Length, 5.3 mm. Width across eyes, 1.35 mm. Color and shape of head 

 practically the same as in preceding instars; lateral angles of first pair of wing 

 pads now reach almost to the apex of the second pair; lateral angles of second 

 pair have now extended farther caudad, making median indentation in caudal 

 margin more pronoimced; do not extend beyond second segment of abdomen. 



