THE. PERIODICAL CICADA 



cessation ot digging and the tarsi are turned forward at 

 right angles to the tibiae to serve as rakes (Fig. 1 1 6 B). 

 The mass of earth pellets is scraped in toward the body, 

 and — here comes the important part, the cicada's special 

 technique — the little pile of rakings is grasped by one 

 front leg between the tibia and the femur (Fig. 116 A, 

 Tb and F), the former closing up against the spiny margin 

 of the latter, the leg strikes forcibly outward, and the 

 mass of loosened earth is pushed back into the surrounding 

 earth. The process is repeated, first with one leg, then 

 with the other. The miner looks like a pugilist training 

 on a punching bag. Now and then the worker stops and 

 rubs his legs over the protruding front of the head to 

 clean them on the rows of bristles which cover each side 

 of the face. Then he proceeds again, clawing, raking, 

 gathering up the loosened particles, thrusting them back 

 into the wall of the growing chamber. His back is firmly 

 pressed against the opposite side of the cavity, the middle 

 legs are bent forward until their knees are almost against 

 the bases of the front legs, their tibiae lying along the wing 

 pads. The hind legs keep a normal position, though 

 held close against the sides of the body. 



From what we know of the cicada's spring habits 

 underground, we can infer that the nymphs construct 

 their chambers on their arrival near the surface during 

 April, and that, when the chambers are completed, the 

 insects wait within for the signal to emerge and trans- 

 form into the adult. Then they break through the thin 

 caps at the surface and come out. It would be difficult 

 to explain how thev know when they are so near the top 

 of the ground, and why some construct ample chambers 

 several inches deep while others make mere cells scarcely 

 larger than their bodies. Do they burrow upward till the 

 pressure tells them that the surface is only a quarter of 

 an inch or so away, and then widen the debris-filled 

 tunnel downward? Evidently not, because the chamber 

 walls are made of clean, compacted clay in which there 



h9>] 



