Miscellaneous. 427 



such are the infinite resources of the Creator, it had grafted, by some 

 mysterious operation, its own stigmata upon one of the two large 

 trachean reservoirs, situated, in the Andrena, as in many other 

 Hymenoptera, at the base of the abdomen. Thus, not only does the 

 Andrena feed with the products of its own nutrition, this larva which 

 an immutable decree has inflicted upon it, but it is compelled to 

 respire for it, — to furnish it, in its own ample aeriferous reservoirs, 

 with all the air necessary for its respiration. 



Thus we pass, from wonder to wonder, to a recent example of para- 

 sitism, the circumstances of which seem fabulous. 



In the summer of 1850, I had pinned in a box several living speci- 

 mens of a weevil which lives on the tops of our pines, — the Brachy- 

 deres lusitanicus. The next day I found in the box some small 

 chrysalids or pupce, issuing without doubt from these weevils. I 

 perceived without difficulty that these pupae, which the unlearned 

 would have taken for little red grains, were the cradles or swathes of 

 a Dipterous insect belonging to the immense family of Muscidce. After 

 a few days I had the satisfaction, always new for my old experience, 

 of witnessing the exclusion of a pretty little new fly, the colouring of 

 which differed in the two sexes. I hastened to publish this double 

 fact, and the fly was christened Hyalomyia dispar. But this was 

 only two-thirds of the history of the metamorphoses of this fly ; — the 

 initial phase, that of the larva, was wanting. The discovery of this 

 I put off to the next year, and I have been able to realise my wishes. 

 I am not going to describe this larva of an eighth of an inch in length ; 

 I shall confine myself to exhibiting, in connexion with parasitism, one 

 of the most interesting facts of organic usurpation. This larva, like 

 that of the Ocyptera previously mentioned, lives outside the digestive 

 viscera, in a cavity without air and without issue. In the vivisection 

 of one of the weevils, I had the rare good fortune to find two larvae 

 of the Hyalomyia. One which was detached and free had two 

 posterior, tubular stigmata, opening to the two lateral tracheae ; this 

 was sufficient to convince me that it had a complete respiratory appa- 

 ratus. The other remained fixed, and I was able to prove, without the 

 slightest doubt remaining on my mind, that one of the stigmata of 

 the weevil had been usurped. There was not here, as in the Ocy- 

 ptera, a supple caudal tube ; the larva was sessile, and its adhesion 

 appeared to be the result of a graft by approach, — a sort of organo- 

 plastia. The two microscopic tubular stigmata of the larva corre- 

 sponded exactly to the respiratory aperture of its host, and thus drew 

 in the atmospheric air directly. 



Figure the agitation, the patience, the active manoeuvres of the 

 Hyalomyia, when, urged on by a mature gestation, she flies to the 

 tops of the pines to place her eggs in the stigmata of the Brachyderes ! 

 Judge of the difficulty of this egg-laying on the wing from the 

 shielded structure of the beetle ! Although of a tolerably large size, 

 it is apterous ; its elytra, soldered together and hard, are closely united 

 by an imperceptible suture to the equally hard walls of the ventral 

 segments. What sharpness of vision, what urgency of maternal in- 

 spiration, must drive the fly to seek the one defect in the armour, to 

 profit by the fugitive moment when the stigma of the beetle is in 



