1900] WHEAT -BULB FLY. 39 



with two black mouth-hooks (see fig. 2, p. 38), wherewith they tear 

 the substance of the plants on which they feed. So far as the above 

 may easily be seen ; but both in their appearance and in their method 

 of attack they so very much resemble the maggots of the " Frit Fly" 

 (Oscinis frit), which feeds in the heart of young Oat plants, that for 

 sure identification (beyond the fact of one being found in Oats and the 

 other in Wheat) a fairly strong magnifier is needed. 



With this it will be seen that (in the case of the Wheat-bulb 

 Maggot) the tail segment projects at the lowest part, and ends in two 

 squarish-ended teeth with flattened edges, placed centrally, with one 

 pointed tooth, and sometimes more, placed outside the central square 

 pair. When seen with a high power, the ends of the central teeth are 

 noticeably notched; and by these characteristics, and by there not 

 being a little bunch of stalked spiracles near the head end, it appears 

 to me that the Wheat-bulb Maggot may be clearly distinguished from 

 that of the Frit Fly. 



Damage, as shown by the failing and sickly appearance of the crop, 

 may be seen early in the spring, and about the beginning of April the 

 maggots are sufficiently advanced in size to be noticeable in the young 

 Wheat within which they are feeding. By the beginning of May full- 

 grown maggots may be found upwards of a quarter of an inch long, a 

 single maggot lying lengthwise in each infested stem, and filling it up 

 nearly to the outside. 



During May the maggots cease feeding, and go into the ground, 

 where they turn to small brown oval chrysalids (see fig. 3, p. 38), from 

 which the little two-winged grey flies may come out any time between 

 the end of May and the beginning of July. 



The only year in which attack was reported to me as very severe 

 was in 1888, in which packets of infested plants were forwarded to me 

 for examination almost every day from about the first week until the 

 end of May. The amount of injury was mentioned by various corre- 

 spondents as sometimes every plant being destroyed for yards together, 

 or a complete failure in various places, and in the Fens " hundreds of 

 acres being eaten off " ; also that near Warrington, " for several miles 

 around, both in Cheshire and Lancashire, the Wheat crops in some 

 fields have been greatly damaged, in some entirely destroyed." * 



It is a very remarkable circumstance in the history of this attack 

 that it has been especially found to follow on fallow, or also where, in 

 some cases, the preceding crop had partially failed, or been so treated 

 as to expose bare soil. 



As this point is very important in considerations of preventive 

 treatment, and it is now a good many years since the attack has been 



* For observations of attack contributed by numerous correspondents, see my 

 Annual Eeport for 1888, pp. 82-88. 



