— 131 — 



full}- grown ; and no trace of the other larvae could be found. I 

 have found in the fields stalks containing two larvae, but these 

 larvae were separated by a joint of the straw. In no instance, 

 after all the joints of a straw had been tunnelled, have I found 

 more than a single larva. It is probable that where more than 

 one egg is laid in a stalk, the stronger larva destroys the others. 



The eggs hatch soon after the\' are laid, and the larvae may de- 

 velope quite rapidly. A larva which hatched from an egg laid 

 on Ma}^ I3tli was on Ma}^ 24th about one-quarter inch (6 mm.) in 

 length, and had bor^^d through the principal joint of the straw, 

 and had also penetrated the upper solid part of the stalk. Four 

 days later another larva, which also hatched from an egg laid 

 May 13th, was found to have tunnelled the entire length of the 

 .stalk in which it was. * 



In no case did I find any e.Kternal indication of the presence of a 

 larva in a wheat stalk until the larva was nearly fully grown, and 

 had tunnelled the stalk down to the first joint. At this time there 

 is frequently a discoloration of the stalks just below the injured 

 joints. This was observed during the first week in July. The 

 wheat had then reached its full height and the grain was in the 

 milk. 



At this time there wasobserved scattered through the field heads 

 of wheat \yhich were yellow and contained no grain. These dead 

 heads corresponded in appearance exactly with those described by 

 Herpin in the extract quoted telow. I carefully examined many 

 of these stalks ; and found that in no case was the injury due to 

 Cephas pyomacus. In most cases the heads had been killed by a 

 species of Thrips which sucks the juice from the stalk, in the tender 

 portion, within the sheat of the upper leaf, just above the upper 

 joint. This causes the stalk to shrivel at this point, and all above 

 the injury to die. This disease of the wheat is similar to the com- 

 mon one of grass ; but the Thrips which produces it is larger than 

 that infesting grass and is further distinguished by having its 

 antennae marked hy dark rings. 



Altliov5gh this saw-fly borer has not been previously observed in 

 this country, itis a well known European species. It li^is been de- 

 scribed by lK)th English and Continental writers ; and in France 

 especially it has been considered a ver}^ serious pest. One writer f 



* See note 4. 



fj. Ch. Herpin, quoted by Curtis in Farm Insects, p. 253. 



