188 Mr. E. E. Austen on the 



(such as SarguSj Chloromyia, and Actina), as well as the 

 agreement in the mode of pu|>ation, has indeed attracted the 

 attention of most autliors who have studied the Hfe-history of 

 the various species. Thus, in 1828, von Roser (foe. cit. 

 p. 188) dechired the larva of Xj/lop/iar/us van'us [Xylomyia 

 varia)^ Mg., to be very similar to that of Stratiomys ckamce- 

 hon, excluding the tubular tail ; Westwood writes (* Intro- 

 duction ' &c. ii. (1840) p. 535):— "The genus SahuJa^ as 

 discovered by M. van Koser and the Rev. F. W. Hope, has a 

 metamorjdiosis exactly like Sargus, the pupa being enclosed 

 within the unaltered larval skin, but the transformations of 

 tlie typical Xy/opliagi are quite different"; Dufour [loc. cit. 

 p. 7 (1847)) states that the larva of Sargus /ieaumurii\ F. 

 (= Chrysonotus hipunctatuSj Scop.), appears to belong to the 

 same class as that of Suhula a'tripes, Diif. ; and Ferris (Ann, 

 Soc. Ent. Fr. ser. 4, t. x. (1870) p. 20G) alludes to the close 

 resemblance in outward appearance between the huvie of 

 Suhula and those of Pachygaster and Sargus. The agree- 

 ment in general appearance and character of the integument 

 between larvae of XyJomyia and those of Chloromyia or Acti'na 

 must in fact strike anyone, and to attempt to argue that such 

 a remarkable external resemblance is due to mere conver- 

 gence, brought about by adaptation to a similar mode of life, 

 is manifestly out of the question. To refute such a sugges- 

 tion it is only necessary to compare a larva of Xylomyia with 

 that of Xylophagus or with any of the other dipterous larvas 

 to be found in the mouldering stumps of dead trees. It is 

 true that the larvae of Xylomyia appear to be amphipneustic, 

 while those of Stratiomyidas in general are peripneustic; but, 

 according to Brauer, the number and position of the stigmata 

 is a very variable character, which lias arisen by adaptation 

 in so far as these apertures are peripheral or merely polar. 

 Moreover, as 1 have shown above, the larva of Xylomyia 

 appears to exhibit distinct vestiges of peripheral stigmata. 



With reference to the importance of insect larvje as indi- 

 cating affinities, Brauer writes * : — *' To contemplate earlier 

 developmental stages of animals is, however, to cast a glance 

 at their pedigree, which is otherwise beyond our reach, and I 

 have already shown in another place (" Betrachtungen iiber 

 die Yerwandlung der Insekten im Sinne der Descendenz- 

 theorie. — II.," Verb. z.-b. Ges. Wien, 1878, p. 151 et seq.) 

 that even such acquired larval forms as those of the insects 

 are adapted fur this purpose because they have become htredi- 

 tary.''^ 



There is no necessity to repeat the arguments (drawn from 

 • Denkscbr. k. Akad. AViss. Wien, Rd. xlvii. (1883) p. 3. 



