186 Mr. E. E. Austen on the 



tubercles. Von Roser states that the segments have " a 

 transverse row of from eight to ten dirty whitish-yellow 

 round tubercles, each of which bears a small bristle of similar 

 colour. A more numerous row of smaller tubercles is more 

 or less distinctly visible at the base of the rings." 



The most remarkable phenomenon presented by Xyhmyia, 

 apart from the striking resemblance of its larva to that of 

 certain Stratiomyida3, is the way in which the imago makes 

 its escape, from the pupa. As in ordinary St.ratiomyida?, 

 pupation takes place within the dried larva-skin (puparium), 

 which, owing to its hardness, doubtless affords an excellent 

 protection ; but, instead of the fly making its escape in the 

 ordinary way from the anterior extremity of the puparium, 

 leaving the pupa-skin behind it within the latter, the pupa 

 itself, shortly before the imago emerges, makes its way partly 

 out of the puparium through a longitudinal cleft which 

 appears in the middle dorsal line of the second and third 

 thoracic and first two abdominal segments. The pupa does 

 not leave the puparium altogether, but its posterior extremity 

 remains fixed in the cleft, and in this position the semi- 

 transparent shining yellowish-brown pupa-skin is left sticking 

 after the escape of the fly, which is no doubt facilitated by 

 the fixation of the pupa-skin. The abdominal segments of 

 the pupa, from the second to the sixth *, bear a transverse 

 row of stiff, appressecl, backwardly directed bristles, reddish 

 brown in colour, and arranged in groups, each group having 

 in the middle a bristle longer than the rest. The function of 

 these bristles evidently is to assist the pupa in raising itself 

 out of the puparium. For a more derailed account of the 

 pupa the reader may be referred to Townsend's description of 

 the pupa of Subula pallipes, Lw. (loc. cit. p. 165). 



The fixture of the pupa (and pupa-skin after the escape of 

 the fly) by the posterior extremity in the cleft in the pupa- 



eegments thoraciques sont tout a fait lisses, taudis que les suivants ont, 

 tout pres de leur bord anterieur, une s^rie transversale de fort petitea 

 asp6rit(5s sous formes de points." The larva of Xylomyia {Subula) 

 citripes, Duf., as described by Dufour himself (ibid. pp. 7-8 ; of. t. vi. 

 pi. xvii. tig. 12), also has transverse rows of tubercles (a single row on 

 the three thoracic segments and a double row — one of very minute 

 tubercles near the anterior margin and another of larger tubercles 

 towards the middle — on those of the abdomen). So far as we can judge 

 at present, therefore, in the absence of tubercles the larva of X. maculata 

 is unique. 



* Townsend [loc, cit. p. 165) writes "segments 2-7 " in the case of the 

 pupa of Subula pallipes, Lw. ; the statement may very possibly also apply 

 to the pupa of X. maculata, but in the specimen before me I cannot trace 

 the abdominal segments back beyond the sixth, as the remainder are 

 hidden in the puparium. 



