Chap. XII.] 



THE MASON WASP. 



417 



instinct. A fossorial wasp of the family of Sjohegidce l 9 

 which is distinguished by its metallic lustre, enters by 

 the open windows, and converts irritation at its move- 

 ments into admiration of the graceful industry with 

 which it stops up the keyholes and similar apertures 

 with clay in order to build in them a cell. Into this it 

 thrusts the pupa of some other insect, within whose 

 body it has previously introduced its own eggs. The 

 whole is surrounded with moistened earth, through 

 which the young parasite, after undergoing its trans- 

 formations, gnaws its way into light, to emerge as a four- 

 winged fly. 2 



A formidable species (Sphex ferruginea of St. Far- 

 geau), which is common to India and most of the 

 eastern islands, is regarded with the utmost dread by 

 the unclad natives, who fly precipitately on finding them- 



1 It belongs to the genus Pelo- 

 pcsus, P. Spinolcs, of St. Fargeau. 

 The Ampulex compressa, which 

 drags about the larvae of cock- 

 roaches into which it has implanted 

 its eggs, belongs to the same family. 



2 Mr. E. L. Layard has given an 

 interesting account of this Mason 

 wasp in the Annals and Magazine 

 of Nat. History for May, 1853. 



" I have frequently," he says, 

 "selected one of these flies for 

 observation, and have seen their 

 labours extend over a period of a 

 fortnight or twenty days ; some- 

 times only half a cell was com- 

 pleted in a day, at others as much 

 as two. I never saw more than 

 twenty cells in one nest, seldom 

 indeed that number, and whence 

 the caterpillars were procured was 

 always to me a mystery. I have 

 seen thirty or forty brought in of a 

 species which I knew to be very 

 rare in the perfect state, and which 



I had sought for in vain, although 

 I knew on what plant they fed. 



" Then again how are they dis- 

 abled by the wasp, and yet not in- 

 jured so as to cause their imme- 

 diate death ? Die they all do, at 

 least all that I have ever tried to 

 rear, after taking them from the nest. 



" The perfected fly never effects 

 its egress from the closed aperture, 

 through which the caterpillars were 

 inserted, and when cells are placed 

 end to end, as they are in many in- 

 stances, the outward end of each 

 is always selected. I cannot de- 

 tect any difference in the thickness 

 in the crust of the cell to cause 

 this uniformity of practice. It is 

 often as much as half an inch 

 through, of great hardness, and as 

 far as I can see impervious to air 

 and light. How then does the en- 

 closed fly always select the right end, 

 and with what secretion is it sup- 

 plied to decompose this mortar ?" 

 E 



