NEMA TO CERA. 53 



•wheat or barley, about eight in a patch, glued together by a sticky 

 fluid. The greater number are deposited on the latest-developed 

 leaves. The eggs are laid with the head end downwards, so that 

 when the larvae are hatched they are prepared to crawl down the 

 leaves and stem, and to establish themselves within the leafy sheath, 

 generally at the second joint above the ground. 



The larva is short, stout, cylindrical, and soft-bodied ; about 

 2 mm. long when young, increasing to about 3 mm. There are 

 fourteen segments, and indications of prehensile feet at the anal 

 end. When first hatched the larvas are transparent, showing the 

 alimentary canal through the extremely thin body wall, often green 

 in colour, owing to the colouring matter of plants. They change 

 colour when pupating. 



The larva, when it has passed its feeding stage, develops a forked 

 appendage, a horny short stem with two little projections, situated 

 close to the head on the under surface of the second segment — the 

 " anchor-process." 



In the case of the fly now under consideration, Mr. Knock has 

 made the notable discovery that the larva, after it has finished feed- 

 ing on the juices of the stem, with head placed downwards and 

 inwards, turns itself completely round in its third stage, bringing its 

 head upwards, anchor-process outwards, and that it uses the anchoi- 

 process to perform this feat. 



This turning movement takes place within the "■ puparium" as the 

 hard case, or skin, is called, which gradually forms itself around the 

 larva, in its second stage, after the first, or feeding stage, is passed. 



This case is chestnut brown, and in size, shape and colour re- 

 sembles a small flax-seed, so much so that this stage in the life-history 

 of the fly is often called the " flax-seed stage." At first the puparia 

 are smooth, but after a few days they become marked by longitudinal 

 striations. There are also transverse markings on these "flax-seeds," 

 showing the old segmentation of the larval body. 



The (^ puparium is narrower and paler than the V • The " flax- 

 seed " stage may only last five or six weeks, or the fly may remain 

 in this state throughout the winter or longer. (The time of emer- 

 gence greatly depends upon climatic conditions, cold greatly retard- 

 ing their development.) 



The larva then works its way out of the puparium, casts its skin, 

 and gradually changes into a true pupa. The true pupa is at first 

 white, then pink, and becomes darker by degrees. It is oval, with 

 rounded ends, the thoracic portion narrower than abdominal, limbs 

 and body before emerging enveloped in separate cases. The pupae 



