More Hunting Wasps 



to doubt. It may be said that experiment, 

 with its artifices, does not succeed in re- 

 alizing the delicate natural conditions. To 

 make short work of all objections, I cannot 

 do better than have recourse to facts in 

 which the experimenter's hand has not inter- 

 vened. The parasites will supply us with 

 these facts ; they will show us how alien the 

 quantity and even the quality of the food 

 are from either specific or sexual characters. 

 The subject of enquiry thus becomes double, 

 instead of single as it was when I plundered 

 one cell in my split reeds to enrich another. 

 Let us follow this double current for a little 

 while. 



An Ammophila, the Silky Ammophila,^ 

 which feeds on Looper caterpillars,^ has just 

 been reared in my refectory on Spiders. Re- 

 plete to the regulation point, it spins its co- 

 coon. What will emerge from this? If 

 the reader expects to see any modifications, 

 caused by a diet which the species, left to 

 itself, had never effected, let him be unde- 

 ceived and that quickly. The Ammophila 

 fed on Spiders is precisely the same as the 



1 Cf. The Hunting Wasps: chaps, xiii. — Translator's 

 Note. 



2 Known also as Measuring-worms, Inchworms, Span- 

 worms and Surveyors: the caterpillars of the Geometrid 

 Moths.— Translator's Note. 



232 



