412 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



The tibia is short and much wider at the lower end than 

 at the upper. The tarsus is slightly longer than the tibia 

 and terminates in a single, rather heavy claw. The coxa 

 has no hairs. The trochanter bears one long hair on the 

 outer side near its articulation with the femur. The femur 

 has several short hairs. The tibia bears several hairs at 

 each end. The tarsus also bears several hairs, and on the 

 upper side a long hair ending in a knob. On the ventral 

 side of the claw near its base are two digitules reaching 

 somewhat beyond the claw and knobbed at their tips. 



Second Stage. — The young grow very rapidly, the most 

 marked change occurring about February i, in the antennas, 

 which become seven-jointed by an elongation and division of 

 the third segment. The formula now is 7, 3, 6, (i, 2, 4, 5). 

 There is no change in the body or legs except the increase 

 in size. The marginal spines of male specimens show 

 distinctly. 



3. Development of the Male (figs. 2, 3, 4). — Those 

 individuals destined to become male flies continue to grow 

 rapidly until about March i, when they are considerably 

 larger than the adult female. The segments of the body 

 are now well developed and distinctly marked. 



The marginal groups of five or six hairs each are now 

 plainly visible on each abdominal segment. On each lateral 

 margin of the eighth segment there is a group of about ten 

 spines, and the marginal tubercle bears one long hair and 

 three shorter ones. On each margin of the thoracic seg- 

 ment are three groups of from six to eight spines each. 

 On the head there is a small group just above each eye, a 

 large group near the base of each antennas, and between 

 the antennas are four smaller groups. 



The antennae are now seven-jointed, formula 3, 7, (i, 2, 

 4, 5,) 6. They are also well supplied with hairs (fig. 2). 



The legs are well developed; coxag, trochanter, and femur 

 being very stout, tibia and tarsus long and rather slender, 

 the tarsus about two-thirds the length of the tibia. The 

 claw is rather longer and more slender than that of the 

 female, and it bears a short conical tooth on the ventral side 

 near the distal end. The claw bears two knobbed digitules 



