129 — 



ings. Fig. i,b. Between tliis plug and the lower end of the cavity 

 of the straw there is a place, measuring about one half inch in 

 length (lo mm. to 15 mm.) Plate, e. It is here that the insect 

 passes the winter. Immediately after cutting the straw and mak- 

 ing this plug the larva makes a cocoon by lining the walls of this 

 space with a layer of silk. Fig. i, a. This layer is thin but very 

 firm and more or less parchment-like ; it can, however, be broken 

 with slight difficulty, being .somewhat brittle. 



Within this cocoon, which remains in the stu1)ble after the grain 

 is cut, the insect passes the winter, in the larval state. It changes 

 to a pupa during March or April* ; and sometime during the 

 month of Ma}' the adult insect appears. 



The exact date of the appearance of the insect depends upon 

 the nature of the weather. This year from pupae collected on the 

 23d of April and brought into the Insectar3^ the adults emerged 

 from the 8th to the loth of May ; while the ins-Cts left in the fields 

 were ten days later in emerging. 



The adult insect is a four- winged fl}- belonging to the order 

 Hymenoptera, the order that includes the bees, wasps, and ants ; 

 and it is a member of the family Tenthredinidae of this order, a 

 family comprising the insects commonl}- known as Saw-flies. 

 This popular name refers to the fact that in this family the female 

 insects are furnished with a more or less saw-like organ. This 

 arises near the caudal end of the bod3\ and is the ovipositor. By 

 means of it the insects are able to make incisions in the tissues of 

 plants for the reception of their eggs. 



The Saw-fly Borer of Wheat, is known to entomologists as 

 Cephtis pygmaeiis. The form and appearance of the adult are 

 represented on the accompaning plate. In this stage it is of a 

 shining black color, banded and spotted with yellow. The male 

 measures one-third inch (8 mm.) in length ; the female two-fifths 

 inch (10 nnn.)t 



Soon after the adults emerge from the stubble, they pair and the 

 females begin to oviposit. Thus in our breeding-cages, the adults 

 which emerged from the 8th to the loth of Ma}^ began to pair on 

 the loth and the females were ovipositing on the 13th. 



The appearance of the insects in large numbers in the field took 

 place four or five days before the heads of wheat began to appear, 

 /. e., before they began to project from the sheath formed by the 



*See note 5. fFor a detailed description see note i. 



