LIFK-niSTORY OF MKTCT;CUS (RIIIPrPHORUS) PARADOXUS. 321 



Sketch of the Life-history of Metoecus (Rhipiphorus) paradoxus. 



By T. A. CHAPMAN, M.D,, F.E.S. 



The editor of the Entomologist's Record having asked me for a 

 sketch of the life-history of Metoecus {Bhipiphorus) paradoxus, I make 

 the following notes, perhaps not an undesirable thing, as my original 

 contributions to the matter, in the Annals and Magazine of Natural 

 Historg, are not very accessible to many entomologists. 



So soon as it leaves the cell in which it is matured, the beetle 

 leaves the wasp nest ; no doubt this statement may require modifi- 

 cation in regard to detention by weather, the observations, on which it 

 depends, being that beetles are not to be found at large in the nest, 

 beyond what may be assumed to have escaped from the cells between 

 the times of taking and examining the nest, usually, in fact, none, 

 occasionally, one or two. At large, they have been taken on flowers ; 

 but their chief occupation is oviposition. The eggs appear to be laid, 

 and the beetles die within a few weeks of their escape. They pair 

 readily in confinement, if placed in the sun with some vegetation and 

 flowers. 



As I failed to get them to lay in captivity, under a variety of 

 circumstances, till I provided them with some half-rotten wood, deeply 

 in the chinks of which the eggs wei'e laid in little groups, I have no 

 doubt that naturally the eggs are laid in the cracks and cavities of 

 posts and other dead timber, such wood, in fact, as the wasps fre- 

 quent to get their wood-pulp for paper-making, probably near the 

 ground to prevent desiccation. 



As I failed to get any eggs to hatch, I do not know the further 

 history, until the following summer, that is, I do not know whether 

 the eggs remain undeveloped all winter ; whether the young larvae 

 develop in the autumn, but remain unhatched till spring; or whether 

 they hatch in autumn, and find suitable hibernacula for themselves. 

 These young larvae are about one-fiftieth of an inch in length, little 

 active black mites, very like the similar stage in Meloe or Sitaris, but 

 shorter and broader. They, no doubt, meet with a wasp and attach 

 themselves to it, when it is collecting paper material, but I have never 

 succeeded in finding a wasp so infested, and only once saw the little 

 mite at large in the nest. It must, therefore, very quickly transfer 

 itself from the wasp that brings it in, to the larva that is its host. 

 This larva is usually about half -grown when the M. paradoxus mite 

 makes its way into the interior of the wasp-grub. It lies bathed in 

 the larval fluids, and lives on these rather than eats anything. Here 

 it may be found, generally in the flanks of the 3rd or 4th abdominal 

 segments, until the time when the wasp-grub forms its cocoon, gradu- 

 ally increasing in size, until it reaches a length of 3-4 mm. The larva 

 has not yet moulted, though it has grown so much, and still pre- 

 serves the black dorsal and ventral plates, head, legs and anal suckers 

 of the small active larva. These are now, however, widely separated by 

 the extension of the intermediate membrane, and give the larva the 

 appearance of an ordinary maggot with series of black marks. It is 

 by aid of these series of marks that the larva may be seen through 

 the skin of the wasp grub. 



When the wasp-larva has completed the silken cap of its cocoon, 

 the young M. paradoxus larva still possesses sufficient command of 



