A. W. Rymer Roberts 127 



the second ecdysis the larva grows a little before the winter and then 

 moults again about April or May of the following year. It is at this 

 stage that the young larvae are generally first recognised in the field 

 and they are then of a length of some 6-5-8-5 mm. 



At the end of the second year of life, after two more ecdyses, the 

 larvae have attained an average length of 10-11 mm., and are then 

 very distinctly yellow. From this stage onwards observations have 

 been made only on wild-caught larvae, but for A. obscurus it appears 

 to be probable that the rate of growth is somewhat as follows : 

 3rd year from 11 mm. to 17-18 mm. 

 4th „ „ 18 „ „ 20-21 „ 

 5th „ „ 21 „ „ 23-25 „ 



Such an estimate tallies with Bierkander's statement (Marsham(i7)) 

 that he had kept the larvae in confinement for five years. Ford ((ii) 

 p. 101) considers this period too long, but as will be noticed from his 

 argument on the subject, he did not take into consideration the small- 

 ness of the larvae in the first year of life — the earliest stage known 

 to him being larvae of 7 mm. in length — nor the fact that growth 

 in the last year is very small. The figures given above are approxi- 

 mate only but are taken from data of measurements of wild-caught 

 larvae together with laboratory observations on their subsequent 

 development. 



The fact does not appear to have been generally recognised that the 

 larvae normally moult twice in the year, in April and May and again 

 between July and September. It appears to be true both for A. obscurus 

 and A. sputator; also for some other species of Elaterid larvae. The 

 summer moult is the most noticeable, since all the larvae appear to be 

 at ecdysis at nearly the same time. At this time the larvae under natural 

 conditions are deep in the soil, possibly as a protection from the appe- 

 tites of those few" which are not in the same condition and of other 

 predaceous insects. The spring moult does not appear to take place 

 amongst all the larvae at one time to the same extent, but there is no 

 doubt about its occurrence. A number of cases have been noted among 

 laboratory-fed larvae; but in addition exuviae, evidently freshly shed, 

 have been found out-of-doors in April and larvae brought into the labora- 

 tory from outside in May have moulted within a short time afterwards. 

 Graf (13) found the same in the case of Limonius calif ornicus, an American 

 pest of sugar-beet, but he records it in rather a tentative manner (p. 30), 

 though evidently expecting that subsequent experience will confirm 

 the results which he obtained in 1912. 



