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ON THE (ECONOMY OF THE CHRYSIDES PAEASITIC ON ODYNEBTJS 



SPINIPES. 



BY T. ALGERNON CHAPMAN, M.D. 



The species of the genus Chrysis are, so far as is known, parasitic 

 on wasps and bees ; those which are attached (apparently, exclusively) 

 to Odynerus spinipes being G. neglecta and bidentata, which are common 

 wherever O. spinipes abounds. G. ignita, the most abundant species of 

 the genus, appears to lay her eggs in the nests of almost any kind of 

 wasp to which she can obtain access, and occasionally visits those of 

 O. spinipes, but is abundant in the nests of Odynerus parietum. G. 

 fulgida has also been recorded (by Mr. P. Smith) as attached to O. 

 spinipes ; but I have never met with it, and suspect that it is the 

 proper parasite of some other and rarer species of Odynerus, and that 

 its occurrence with 0. spinipes is accidental, in the same sense as that 

 of G. ignita may be said to be so. I may remark, that I was quite 

 unprepared to find G. ignita so rare as a parasite of O. spinipes ; as, 

 though often to be seen about the burrows of that insect nearly as 

 plentifully as G. neglecta or bidentata, out of more than a hundred 

 Chrysis cocoons collected last winter, I found only one of 0. ignita ; 

 and this summer I have seen only three of its cocoons in the cells of 

 O. spinipes. The destruction caused by Ghrysides amongst the young 

 brood of 0. spinipes, roughly measured by the cocoons collected last 

 winter, is in the proportion of one to three of those of the wasp ; the 

 proportion of G. neglecta to G. bidentata being as three to two. 



On July 17th, I observed a nest of O. parietum with one cell open 

 and containing a nearly complete supply of Lepidopterous larvae. A 

 Chrysis ignita, flying about, settled beside the cell ; and, after a brief 

 examination with her antennas, wheeled round, and, introducing her 

 abdomen into the cell, rested for about twenty seconds, doubtless in 

 the act of oviposition. I now regret that I did not then examine the 

 contents of the cell, in order to ascertain the fate of the egg of O. 

 parietum. Three-quarters of an hour later, O. parietum had closed the 

 cell with the usual earthen pellets. Two days afterwards, I examined 

 this cell, when I found a larva of G. ignita a quarter of an inch long, 

 together with the Lepidopterous larvae stored by the wasp, but there 

 was no trace of either egg or larva of the latter. On the 23rd, six 

 days from the date of oviposition, the Chrysis larva had eaten all the 

 store, and was full-fed. I obtained evidence, by finding the exuviae, of 

 its having cast its skin three times, whilst under observation ; and, 

 from the analogy of G. bidentata, I believe it had clone so four times 



