l^Q DR. V. B. SHELFOKD ON THE LIFE-HISTOKIES AKD 



2. There are three larval stages ; the first usually lasts a little more than 

 one month and the others vary greatly in difEerent species, (p. 161.) 



3. The burrows differ greatly in different species ; generosa has a burrow 

 which opens into the side of a pit, an adaption to shifting sand (p. 165) ; 

 cuprascens does not smooth the edge of the burrow in the usual manner 



(p. 169). 



4. The life-histories are of three types : — 



(a) Eggs laid in the late spring or early summer ; larvae hibernate 

 usually in the third stage, pupate in the second summer ; imagoes emerge 

 about a month after pupation, hibernate, and become sexually mature 

 late in the third spring, — larval life lasts twelve to thirteen months, 

 adult life ten months, — two years between generations, (pp. 161-167.) 



(6) Eggs laid in mid-summer ; larvse hibernate usually in the third 

 stage, pupate in the following June ; imagoes emerge in early July and 

 become sexually mature very soon, — larval life ten months, adult life two 

 months, — one year between generations, (p. 168.) 



(c) Eggs laid in mid-summer ; larvse hibernate in the second stage, 

 reach the third stage early in the second summer, hibernate again, and 

 pupate in the following May ; imagoes emerge in the early part of the 

 third summer and become sexually mature soon, — larval life twenty- 

 one mouths, — adult life two months, — two years between generations, 

 (pp. 168-169.) 



5. Temperature, moisture, and food influence the length of the different 

 stages, (p. 176.) 



6. Pigmentation and final hardening of the cuticula take place in the pupa 

 in those parts which are employed in the final ecdysis and the bristles of the 

 imago assist in the removal of exuvium. (p. 163.) 



7. The generations frequently overlap : of importance in connection with 

 colour-changes to be discussed later, (pp. 164 & 167.) 



8. The habits and responses of the imagoes and larvse bring about great 

 differences in the environmental conditions of different individuals of the 

 same brood, (pp. 176-179.) 



This work is a part of investigations which were begun at the Hull 

 Zoological Laboratory, the University of Chicago, in 1903, and which are 

 still being carried on with the facilities afforded by this institution. It gives 

 me pleasure to acknowledge my indebtedness * to the staff of Zoology of^this 

 institution, for much kindly advice and enthusiastic encouragement. 

 September, 1907. 



* The Author wishes to acknowledge his indebtedness to Mr. C. J. Gahan ; also to Mr. R. 

 Shelford, Canon W. W. Fowler, and Professor Poulton for courtesies in connection with the 

 presentation of this paper to the Linnean Society ; and finally to Dr. W. Horn for calling 

 attention to several obscure papers. 



