43 



(.ojiinionest species. The adult beetles hatch from the pupa in 

 August or vSeptember and remain in hibernation during- the winter. 

 About the middle of May they emerge, feed on the nectar or pollen 

 of flowers and do little or no damage, at least in this country. 

 Oviposition takes place generally from the end of June to the 

 middle of July. The eggs of three species of Agriotes — ohscurus^ 

 spiitator and sohrinus and Athous hcemorrhoidalis were 

 obtained from the soil of pots, in which the beetles had 

 been confined, at depths varying from |-inch to 2 inches, either 

 in batches or singly. Attempts to obtain ova from Ag. lineatiis 

 failed, but from other sources it is known to deposit its eggs in a 

 similar position, and probably the presence of grasses, whether 

 cultivated or grow ing as weeds, is essential to all five species. This 

 conclusion points to the necessity for clean cultivation in the con- 

 trol of wircworms. 



The larvaj on emergence at once burrow into the soil. All are 

 pale in colour and so small (1-2. 75mm.) as not to be generally 

 recognised during their first year. The first moult of A. obscurus 

 takes place in Jur.e, the second in July or August, and it is believed 

 that the larva^ in general moult twice a year, in April or May, and 

 again between July and September. In their first year, the larvae 

 appear to feed chiefly on partially decomposed vegetable matter 

 and perhaps to some extent on the small roots of living plants, but 

 no evidence of definite damage was obtained. In the later stages 

 they feed on almost any crop and on many weeds. They appear 

 to attack mustard only in the absence of more suitable food, 

 tliough they are frequently found at the roots of charlock. The 

 larva? can subsist for a long time on the decaying organic matter 

 in the soil and are able to withstand immersion in water for pro- 

 longed periods. During the winter they may be found close to the 

 surface in grass land. But in fallow land they undergo a period 

 of hibernation, sometimes as much as 2ft. from the surface. 



Agriotes ohsciiriis has a larval life history extending to five 

 years, as was originally stated by Bierkander. 



l^ipation takes place in an earthen cell prepared by the larvae 

 at a depth of from 1 inch up to 7i or more inches. The pupal 

 stage extends over a period of about 3 weeks, pupae being found 

 from the end of July to the middle of September. 



Wireworms under natural conditions are not parasitized to 

 any great extent. A Proctotrupid, probably PhcBnoserphus fus- 

 cipes Hal. was bred from Athous hccDwrrhoidalis, and a Procto- 

 trupid was also found within a larval Agriotes obscurus. The 

 latter species was also found to be the host of a fungus of the 

 genus I sarin. 



XXI. F. Tattersfield and A. W. R. Roberts. '' The 

 Influence of Chemical Constitution on the Toxicity of 

 Organic Compounds to Wireworms." Journal of 

 Agricultural Science, 1920. Vol. X. pp. 199-232. 



The relationship between chemical constitution and toxicity to 

 wireworms of organic compounds is found to be of a two-fold 

 nature. 



The general effect of a group of compounds of the same type 

 is directly determined by the chemical constitution of the type. 



