
No. 428.] THE METAMORPHOSIS OF SISYRA. 621 
Fig. 8 gives a comparative view of the larval and adult leg, 
and a view of the lower side of the foot of the adult, showing 
the arrangement of claws and pulvilli, and the four large spines 
on the inner side of the first four joints of the tarsus. Similar 
spines occur on the lower end of the tibia. The larval leg has 
but one claw and a one-jointed tarsus. The legs of the larva 
are all similar. Those of the adult differ considerably; the 
fore legs are thé shortest pair but have the coxa of unusual 
length, nearly equal to the tibia; in the middle leg the femur 
is the longest joint; in the hind leg the femur and tibia are of 
equal length. In all the adult legs the trochanter is much 
narrowed at its distal end where it 
articulates with the coxa. 
Before the pupal stage is reached, 
the legs pull entirely out of their 
chitinous covering, and the process 
of making over begins. In speci- 
mens lightly stained with borax car- 
mine the adult legs can be distinctly 
seen developing under the old chitinous covering. This process 
is shown in Fig. 9, the coxa, trochanter, and femur of the adult 
leg being fully developed, while the tibia and tarsus with its 
five joints are only partially differentiated. The process of 
development for the antennz and mouth parts of the adult is 
very similar to that of the legs, except that these adult organs, 
being so much larger than those of the larva, are early with- 
drawn entirely out of their slender chitinous sheaths, and are 
developed underneath the larval cuticle. 

Fic. 9. — Leg transforming. 
INTERNAL ANATOMY. 
Fig. 10 is a diagram of a sagittal section of the larva through 
the median plane. The position of the brain in the prothorax 
has been noted in some other insects. In the very young larva 
the brain occupies the normal position in the head, but, as the 
pupal stage is approached, it gradually draws backward until it 
occupies the position in the thorax shown in Fig. 10. The 
prothorax also contains, besides its own, the subcesophageal 
