1 76 Relation of Grass Insects to Cultivated Crops 



In 1918 a "slight attack in combination with Oscinis frit" is re- 

 corded (i) at Ormskirk, while at Harper Adams Agricultural College 

 there was an attack on "Square Heads Success" wheat. Theobald 

 mentions the second brood as attacking couch and timothy grasses, 

 so far, however, I have not taken it on timothy. AUied to the foregoing 

 are species of Cecidomyia which were found in great numbers on decaying 

 vegetation during the winter. The "red maggots" accompanied "frit" 

 and "Apamea" in their attacks on wheat and grasses. Larvae were 

 taken on couch, cocksfoot, golden oat and perennial rye grass — the " red 

 maggots" so characteristic are perhaps more saprophytic than parasitic 

 in habit, especially is this so with cocksfoot grass. 



The Frit Fly, Oscinis frit, was found first on November 19th when 

 twelve larvae were taken from one plant of Arrhenatherum avenaceum 

 — the tall oat grass. The plant was growing in the hedgerow bordering 

 a field in which oats were badly attacked previously, so evidently the 

 autumn brood had been egg-laying in the neighbouring grasses. Later, 

 larvae were found feeding in perennial rye grass, golden oat, Holcus 

 lanatus and Agrostis Stolonifera. In early February an attack, previously 

 mentioned, on wheat after "seeds" was noted in a field oh the College 

 Farm and on examination the following infestation was calculated: 

 Plants "Fritted," 27 per cent; plants attacked by Apamea spp., 1-05 

 per cent. In several cases two "frit" larvae were found feeding in the 

 same stem. Regarding burying "frit" and their migration, eight "frit" 

 larvae in situ in wheat plants were buried at a depth of 4 inches in a 

 9-inch pot of medium loam and above were planted four healthy wheat 

 plants and four oat seedlings with the second leaves showing. Though 

 the pot was kept under constant observation none of the plants were 

 attacked but grew vigorously and healthily and no perfect insects were 

 observed to emerge. Collin (5), however, notes emergences from larvae 

 buried from 7 inches to 9 inches deep. 



Of root-feeders there were noted Pachyrrhina imperialis Mg., Tipula 

 oleracea and the larvae of a Sciarid. The first-named feeds on plants in 

 general, in the more moist parts of the field, preferring the rank growth 

 near hedges, though it was found feeding amongst the roots of itahan 

 rye grass growing amongst beans. The larvae of Tipula oleracea, the 

 common "Leather Jackets," were very destructive to barley seedUngs 

 in spring on newly broken-up grass fields of a moist character the soil 

 of which was sandy and humic overlying clay. They are universal feeders 

 and Roebuck (I) calculated in three different grass-fields 220,000, 13,000 

 and 120,000 larvae per acre. 



