Vol. XXIV. April, 1913. No. 5 



. 



BIOLOGICAL BULLETIN 



THE LIFE HISTORY OF DESMOGNATHUS FUSCA. 



(Continued from March Issue.} 



INEZ WHIPPLE WILDER. 

 THE AQUATIC LARVAL PERIOD. 



Following the brief but very important terrestrial larval 

 period, the aquatic larval period begins. As may be computed 

 from the limits of dates during which egg-laying occurs (June I to 

 Sept. i), the probable duration of incubation (5 weeks), and the 

 somewhat variable period of terrestrial life (i to 2 weeks), the 

 date of the beginning of the aquatic period can hardly be earlier 

 than the middle of July or later than the middle of October. I 

 have personally never known of aquatic larvae being found 

 between June 17 and September I. By September 15 they are 

 present in the brooks in great abundance, the majority of them 

 with yolk still present in the intestinal walls, a condition not 

 unlike that shown by stage F of the terrestrial larvae and never 

 as yet found by me in specimens collected in October. These 

 facts point to early September as the time when the majority 

 of the larvae reach the water and begin their aquatic existence. 

 The wide range of variation in the size and proportions of 

 larvae during September and October (cf. Table II. and Graphs 

 III. and IV.) represents the inevitable difference in age resulting 

 from the long period of egg laying. 



As to the duration of the larval period, we have the statement 

 of Reed and Wright ('09): "The larvae transform from Sep- 

 tember to December, when they are from 1 8 to 20 mm. long." 

 My own observation does not confirm this statement. It is a 

 very significant fact that after the larvae once appear in the 

 water in September, they are found about equally abundantly 



293 



