124 



On the Life History of " Wirewonns" 



their death, no ova have been discovered before the early days of July. 

 From a comparison of the time of hatching of some of the ova with that 

 of the maximum incubation period (which is about one month) it would 

 appear nevertheless that some of the eggs are laid in June. 



Ova of both A. obscurus and A. sputator have been found in burrows 

 excavated by the beetles in the soil, in one case the burrow appearing 

 to be more or less horizontal, in another vertical. It is possible that this 

 may be commonly the case but the friability of the soil when it is ex- 

 amined renders it uncertain whether the burrow will remain intact. 

 The friability of the soil also makes it difficult to say whether the eggs 

 are always laid in clusters. Certainly this is frequently the case, 52 eggs 

 of A. obscurus having been taken in close proximity, but many have 

 also been taken singly and in twos and threes and these have almost 

 certainly not always been detached from larger clusters. In the case of 

 A. sobrinus, only a few eggs have yet been taken and no clusters were 



Fig. 1. Coherent ova of Agriotes sobrinus, Kies. Magn. x 50 approx. 



found, but in the cases of each of the other two species of Agriotes 

 observed, as well as in that of Athous haenwrrhoidalis, clusters of eggs 

 have been found. 



The eggs in a cluster do not generally cohere at all fast, and no 

 evidence has been forthcoming that they are in any real sense glued 

 together, or to the soil in which they are laid, by any special material 

 produced by the mother for the purpose, as is the case with some insects. 

 Text-figure 1 is an outline drawing showing three eggs of Agriotes sobrinus 

 which were coherent when dug up from the soil. One of them, which 

 appeared to have cohered to the others in a plane at right angles to 

 their long axes, eventually became detached under manipulation. 



The actual environmental condition necessary for oviposition is a 

 matter of the greatest practical importance and it is one which cannot at 

 present be considered entirely solved. It seems from extrinsic evidence 

 however to be probable that the presence of grasses, either cultivated or as 

 weeds, is nearly, if not quite, an essential factor. Thus the tj'pical situa- 



