200 THE SOLITARY WASPS. 



CHAPTER XY. 



EXTRACTS FROM MARCHAL'S MONOGRAPH ON CERCERI& 

 ORNATA. 



The memoir of Paul Marchal on Gerceris oniata^ contains 

 so much that is of interest that a series of short quotations from 

 it would quite fail to give an idea of the thoroughness of the 

 work upon which it is based and of the importance of the re- 

 sults. "We therefore take the liberty of transcribing freely a 

 considerable part of the paper. 



The nest of the wasp consists of a tortuous galleiy from 

 which lead a number of rounded cells. In each of these is de- 

 posited an egg with enough bees of the genus Halyctus to nour- 

 ish it through the larval stage. The pro"vdsioning of one cell 

 is completed before that of another is begun, so that in a single 

 nest there may be found one cell partly provisioned, one with 

 an egg and others in different stages. The egg is placed diago- 

 nally on the ventral face of the thora:?. A single cell contains 

 a variable number of victims — some seven or eight, others four 

 or five. Probably those of a small number are destined for the 

 males. The species of Halyctus used are numerous, and male 

 bees are often found among the victims, some cells having noth- 

 ing else. 



Cerceris ornata is one of those wasps that are not disturbed 

 by artificial conditions. When placed with a bee under a bell- 

 glass her method may be studied in detail. It is only necessary 

 to have patience — in a quarter or half an hour she comes near 

 Halyctus and engages in combat. If one has laid in a sufficient 



*Etude sur I'lnstinct du Cerceris ornata. Archives de Zoologie Exper- 

 imentale et Gen6rale, Deuxieme Serie, Tome. Cinquieme, 1887. 



