170 



OBSERVATIONS ON THE INSECTS OF GRASSES 

 AND THEIR RELATION TO CULTIVATED CROPS 



By HERBERT W. MILES, N.D.A., Dip. Agr. (Harper Adams). 

 From Harper Adams Agricultural College, Newport, Shropshire. 



I. INTRODUCTION. 



The insects of grasses may be divided into two distinct groups, those 

 which actually feed on the grasses and those which shelter among grass 

 during the winter period. For the purpose of this paper particular em- 

 phasis will be laid on such insects as, while using grasses for shelter or 

 food, finally migrate to cultivated crops for the completion of their life- 

 history, for the development of later broods, or, as in the case of shelter- 

 ing insects, for food when the crop is at the critical stage which satisfies 

 their requirements. 



That insect pests of cereals use grasses as intermediate hosts is a 

 well-estabUshed fact (see Theobald (18), Miall(ii), Washburn (19) and 

 Lugger (10)). So far, however, Httle attempt has been made to establish 

 definitely the part played by grasses in harbouring the pests, and we 

 know very little of the degree of infestation of those which grow about 

 our hedgerows and waste places. Accurate knowledge under this head 

 would be of value to the agriculturist in controlling insect pests by the 

 more efficient upkeep of hedges and ditches. 



This subject for investigation was suggested by Dr A. D. Imms, M.A., 

 to whom I am grateful. My thanks must also be expressed to Mr A. 

 Roebuck, Head of the Department of Agricultural Biology at Harper 

 Adams College, for information, suggestions and constant advice. The 

 observations were taken over the period from mid- October 1919 until 

 the end of June 1920. 



The winter period was very mild and undoubtedly favoured the per- 

 sistence of growth of plants and the continued feeding of many insects. 

 The spring and early summer, however, was wet and cold with short 

 periods of bright warm days, which state was so unfavourable that it was 

 not until May 18th that the Frit Fly adults were observed on the oat 

 crop. 



