784 • MR. J. G. 11. FUEW ON THE LAUVAIi 



Inthoduction. 



The following paper deals with the preliminary work done m 

 the course of an investigation on the life-hibtory, possible means 

 of control, etc., of Chlorops tceniopus, the gout-fly of barley. 

 The investigation was commenced in October 1921 under the 

 direction of Dr. A. D. Imms. At the beginning of the work a 

 search was made through the literature of the subject to find 

 a recognisable description of the larva of Chlorops, but no such 

 description could be found. Gout-riy is usually easily recog- 

 nisable by the type of damage which it causes to the barley (or 

 other host-plant). This, however, is not always the case and ono 

 has, fairly frequently, to depend on the morphology of the larva 

 itself for certain diagnosis of the cause of damage to the host- 

 plant. A description of the morphology of the larva seems there- 

 fore to be desirable, as relatively little is known concerning the 

 morphology of Acalyptrate larviB... The. internal anatomy of the 

 larva of Chlorops is also dealt with in this paper. 



During the winter 1921-22 an extended series of examinations 

 of various grasses was made primarily in order to discover the 

 winter hosts of the gout-fly. During this grass examination 

 several other Acalyptrates besides Chlorops were bred out, and the 

 larval forms of two of them are described briefly at the end of 

 this paper. Although these larvte normally pupate within their 

 host they will, if removed towards, the end of their larval period 

 when they have finished feeding, pupate and complete their 

 emergence if placed on iiioist filter-paper in glass tubes. In this 

 way one can be quite certain.. which jaxva is bemg bred out. 



For the iiwestigation of the internal anatomy of the larva of 

 Chlorops both dissections and serial section.s were made. A certain 

 an)ount of the internal anatomy of the larva can bo made 

 out in a living larva in a drop of salt solution, a method useful 

 in checking lesults obtained by other means. 



I wish to express my indebtedness to Dr. A. D. Imms for 

 help and advice in all . branches of this investigation. To 

 Dr. W. E. Brenchley I am indebted for her kindness in 

 identifying all grasses examined during the difficult winter 

 period when only the vegetative characters were available. 

 For the identification of the imagines bred out I have to thank 

 Mr. J. E. Collin. 



CULOIIOPS TiENlOPUS Meig. 

 A. Externcd Anatomy of Larva. 



The following description applies to the third instar larva of 

 either the winter or summer generation ; the points in which the 

 first and second instars difler anatomically from the third will be 

 indicated later. 



The ful]-i>rown larva (text-fig. 1) is approjfimately cylindrical, 

 about 6'3nuii. long and 1*2 mm. in diameter in the posterior 



