H2 BrllnjlontHi Lrnf-Miner 



region of the head loses its flexibility, and becomes more or less rounded. 

 There is then a period of contraction when the fly remains motionless. 

 The abdomen shortens gradually until it has attained its natural size, 

 whilst the head and thorax also become visibly smaller. By this time 

 all the parts have assumed their fundameiital colours. The complete 

 operation occupies about an hour. 



The adults live for about two weeks but, in confinement, when fed 

 on a solution of sugar, they will live for as long as three weeks. 



From a consideration of the foregoing remarks on the life-history 

 of P. Jii/osctjaini, a fairly definite idea may be got of the time that elapses 

 for the various stages of development in the north of England during 

 midsummer : 



DAYS 



Time intervening between the issue of the adult and oviposition 4 



Egg period . . . . . . . . . . . . . . . . 5 



Larval period 



First stadium . . . . . . . . 24 hours ) 



Second ,, .. .. .. .. 48 hours > 10 



Third ,, . . . . . . . . 7 days j 



Pupal period . . . . . . . . . . . . . . . . 17 



Average time for one brood . . . . . . . . . . 36 



There are at least three broods per annum, but there is a good deal 

 of overlapping of the various stages owing to differences in the times of 

 emergence so that eggs, larvae, pupae and adults are all found to occur 

 simultaneously from June to September. 



8. The Buccal-Pharyngeal Apparatus. 



The complete masticating apparatus of the mature larva of P. ht/o- 

 scyami (PI. I, fig. 15) consists of a number of paired sclerites, the members 

 of each side articulating with one another to form a united whole. In 

 the younger larval stages the form of the apparatus is essentially similar 

 to that of the fully-developed larva, the difference being one of degree 

 and not of kind. Each moult sees a strengthening of the chitinous 

 structure. 



The strong tooth-like hooks which are seen projecting when the 

 larva is feeding are the mandibular sclerites (nid.s.) provided ventro- 

 laterally with four small teeth and with a blunted dentate process 



