178 Relation of Grass Insects to Cultivated Crops 



Hymenoptera: 



Pachynematus clitellus | ^ Poa trivialis 



Dolerus haematodes j ( Arrhenatherum avenaceum 

 Lepidoptera : 



Odonestis potatoria . Dactylis glomerata 



Hepialus humuli . Lolium italicum 



Arctia caia . . Dactylis glomerata 



DipUra: 



Agromyza nigripes . Agropyrura repena 



Rhyphnus fenestralis . Lolium talicum 



During the summer perio^ttacks on both grasses and Cereals were 

 noticed by wireworms, leather jackets, surface larvae, weevils and apions. 

 Since most of these insects have been dealt with under the previous 

 section only those not mentioned there will here receive consideration. 



Rhizotrogus solstitialis is a general feeder in the larval stage and like 

 other chafer grubs does damage on broken-up grasslands and to the 

 crops taken after clovers, following up the ravages of Cockchafers. The 

 first " slugworm-Uke '' larvae of Lema melanopa were observed in 

 June 16th feeding on oats. In the same field last year large numbers 

 were noticed attacking the wheat. In 1917 ''Lema melanopa L. was 

 noticed as very abundant on wheat in Kent and Shropshire in July. 

 This insect is often mentioned in connection with cereal crops abroad 

 but in this country seldom attracts attention (i)." 



Regarding the two Sawflies, Pachynematus and Dolerus — in June 

 1919 ten larvae were taken feeding on the leaves of wheat — they were 

 placed on a wheat plant growing in a 9-inch pot and covered with muslin 

 — and finally the greater number pupated. They remained undisturbed in 

 the soil until the early summer, 1920, when from May 10th to 13th four 

 emergences occurred. The first to emerge died but the next two were 

 put on an oat plant under a bell- jar and soon ovipositing was in pro- 

 gress. The larvae from these eggs hatched, but owing to a mischance 

 escaped and were lost. Shortly after (June 13th) a similar larva (8 mm. 

 in length) was taken on the tall oat grass and on July 5th a fully-fed 

 one measuring 18 mm. was found on a similar clump of tall oat. The 

 sites where the larvae were found both in 1919 and 1920 are identical. 



Among the Diptera, Agromyza nigripes'^ was first observed on June 

 17th when eight larvae were found mining the leaves of three wheat 

 plants. In 1919 they were observed feeding exclusively on wheat plants, 

 but in 1920 they seemed to have extended their sphere of activity and 

 numbers were found on oats and couch grass. Larvae taken in June 



1 Very kindly identified by Mr J. E. Collin. 



