100 The Larcal and Pupal Sttu/cx 0/ Agriotes ol)scuriis 



The greater part of the laboratory work has been carried out in the 

 Department of Agricultural Entomology of Manchester and I am also 

 much indebted to Professor Hickson for affording me various facilities. 

 Acknowledgment has already been made to Dr Tmms. I am also 

 indebted to Mr J. T. Wadsworth for the photograph of the pupal cell 

 with the pupa in situ. Mr J. C. F. Fryer of the Board of Agriculture 

 has kindly given me information as to distribution, etc., of the common 

 wire worms. The work has been carried out during my tenure of a 

 Board of Agriculture studentship and completed during the following 

 year. 



3. Notes on the Biology of the Larva. 



The larval stages of Elateridae are practically ubicjuitous, occurring 

 in all types of S(ul. The larvae of Agriotes obscurus have been found 

 most commonly in the ligiiter types of soil, particularly loams rich in 

 organic matter. The range of soils that they inhabit is extraordinarily 

 varied, including the grades between fairly stiff clay to light loam. 

 They are practically always to be found in pastures, even when on clay 

 soils, though in such a case they are much less plentiful. In Cheshire 

 and Lancashire the comnujn wireworm is the larva of A. obscurus, as 

 was demonstrated by breeding experiments. This seems to be corro- 

 borated by the fact that Newstead records adult A. obscurus (when in a 

 state permitting of identification) far oftener than that of A. lineatus, 

 as being the common species taken as food by wild birds over the same 

 area. Very probably, A. obscurus is the common species in the north 

 of England; while A. lineatus seems to be the most common species 

 further south, though A. obscurus and A. sputator are not far behind 

 in point of numbers. An interesting feature with regard to A. obscurus 

 is, that the occurrence of its larvae seems to be, in some way, closely 

 connected with the presence of organic matter in the soil. The larvae 

 are most abundant in soils containing a large percentage of humus, 

 due either to the peaty nature of the soil, or to heavy manuring. The 

 same thing was found in cottage gardens, which are usually very rich 

 in organic matter. This point will be considered later in connectioji 

 with the feeding habits. 



The larvae of A. obscurus were found in what may be roughly 

 described as three stages. These stages were, of course, not sharply 

 defined, but merged into one another. They may be given approxi- 

 mately : 



Small stage (1) 7 mm. long by 0-75 mm. broad. 



fc 



