1916] 



Hyslop — Profhetely in the Elaferid Genus Melanotus 



to believe that an abnormal humidity factor at or shortly before 

 the time of pupation is the causative stimulus of this phenomenon. 

 The accompanying plocted curve (Fig. 1) indicates the period 

 in the activity of the series, when the individual in question 

 transformed to the abnormality herein described. The cages 

 had all been examined on September 3. In examining the cages 

 September 8, the prothetelous larva was discovered. This was 

 a period of minimum moulting immediately preceding a very 

 abrupt and extensive moulting period. The moulted skin of this 

 larva was perfectly normal in every respect and, by careful com- 

 parative measurements, was found to be very nearly identical with 

 the last larval skin; that is, the skin shed when a pupa is formed 

 under normal conditions. The table (Fig. 2) shows the measure- 



CL, 



Length of dorsum of 9th abdominal segment . . 

 Width of dorsum of 9th abdominal segment. . 

 Length of dorsum of 1st thoracic segment. . . 



2.782 

 1.979 

 1.498 



3.103 

 2.193 

 1.819 



3.15G 

 2.193 

 1.712 



Fig. 2. Table showing comparative measurements of larval skins of penulti- 

 mate instar, ultimate instar and prothetelous larvae. 



ments of this cast skin as compared with a larval skin from the ulti- 

 mate and penultimate instar. 



This prothetelous larva is (Plate II, Figs. 3, 4, and 5) predomi- 

 nantly larviform. The abdomen is typically so and normally 

 chitinized, with the exception of a pair of membranous papilliform 

 areas on the posterior margin of each sternitte except the ninth 

 (Plate III, Fig. 3). The thoracic stierna are membranous except a 

 triangular area on the prosternum (Plate III, Fig. 5), which is nor- 

 mally chitinized. The membranous areas are decidedly protuberant. 

 The coxiti and trochanters are larviform with typical pupiform 

 femora, tibiae and tarsi. The ventral part of the protergite is 

 membranous and very much expanded posteriorly. A pair of 

 anterior and a pair of posterior papillae are borne on the spiracular 



