CORN SAWFLY. 95 



The first sign of coming Sawfly attack consists in the flies 

 being observable on the stems or heads of various kinds of 

 Corn or Grass early in the summer. On the 28th of June in 

 1887, the year of the most serious attack of this insect of 

 which I have record, Mr. T, P. Brand, of Brook Hall, near 

 Long Melford, forwarded me specimens, with the information 

 that he had caught them off his Wheat on the previous evening 

 and seen many more. 



The method of attack is for the female by means of her 

 ovipositor to pierce the Corn-stem, just below or at one of the 

 knots, and there insert one egg, continuing this process suc- 

 cessively to other straws, till her egg supply is exhausted. 



The maggot, which hatches in about ten days, is of the shape 

 figured opposite at 4 and 5, about half an inch long, yellowish 

 white, fleshy, with a horny rusty coloured head, and is 

 peculiar in being footless, although the larva of a Sawfly. At 

 the extremity of the tail is a tube-like appendage or extensile 

 tip, which helps the maggot in its progress along the inside 

 of the straw. It feeds on the soft inner substance, clearing 

 its way sometimes through the knots, sometimes even through 

 the topmost, and when nearly full-grown comes down inside 

 the stalk on which it has fed ; and about harvest time, or a 

 little before, it comes down to ground level, where it gnaws a 

 ring so neatly and cleanly round inside the stem, that the 

 straw readily falls with its own weight, or from slight pressure 

 of the wind, the severed stalk showing almost as smooth a 

 fracture as if it had been separated by a knife. When the 

 maggot has thus travelled down the stalk and nearly cut it 

 through (so that nothing may prevent its escape presently as 

 a fly), it goes down into the lowest part and spins itself a 

 silken case, in which it passes the winter. It changes to a 

 pupa in the early summer of the following year, and comes 

 out as a fly, just in time to attack the new croj^s. 



The fly (see fig.) is four-winged, black, and more or less 

 marked or spotted with yellow on the head, abdomen, and 

 legs. The yellow is bright in the male ; more of a sulphur 

 or ochre-colour in the female ; and the wings are iridescent in 

 the male ; more smoky in the female. 



These infested stalks may be known, in the growing crop, 

 partly by the thin white ears standing upright and empty, or 

 with few perfect grains ; * whilst the healthy plants are still 

 green, and in some degree bending with the weight of the 

 head ; partly also by the stalk in some cases containing saw- 

 dust-like excrementitious matter consequent on the Sawfly 



* There is another Wheat attack (known as " White-ears ") somewhat 

 resembUng that of Sa\Yiiy in the appearance of premature ripening. For 

 description of this see note ai)pended to paper on " Thri^DS." 



