Dipterous Genus Conops. 291 



It may readily be conceived that the Conops may in like manner 

 derive some facility in assaulting this formidable Pompilii.s at the 

 moment when the latter may be intently engaged in conveying 

 pabulum into its larva-cells ; or, perhaps with greater probability, 

 that access between the dorsal folds of the latter may be obtained 

 by the former at the period when the Pompilits, first appearing 

 upon the scene of life in the imago state, may be less capaMe of 

 defending itself from attack, its segments less firmly united, and 

 their interstices more exposed to such aggression ; the design 

 accomplished by such parasites in the great scheme of Creation 

 offering, on a comparison between the two cases, more distinct 

 results in the latter, where no progeny of the Vompilus would be 

 produced at all, nature thus impo-.ing limitations and compensatino' 

 influences, to provide against any inordinate increase of the species, 

 whether by restrictions imposed upon larva development, or, as 

 in this instance, by impediments to the subsequent continuity of 

 the line of succession in the perfect insect ; ever delighting in 

 variety for the attainment of her ends, and adapting her resources 

 according to the impalpable peculiarities and exigencies of each 

 particular case. 



I should add that I once found a specimen of the Conops larva, 

 presenting no perceptible difference from the others, within the 

 abdomen of a large Sphex {S. Jlavipennis), capturecl at the same 

 time and place with the Pump'iU; and that I have likewise obtained 

 a smaller species of Conops from the abdomen of an Odijnerus 

 (Div. Ancistrocerus, of Westmael), which had reiDained neglected 

 in a pill box until the following year, as would seem to have been 

 the case with the Bomhi adverted to by Latreille. 



