Chap. XII.] 
THE MASON WASP. 
417 
instinct. A fossorial wasp of the family of Sphegidce l , 
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- 
ypceus, P. Spinolce, of St. Fargeau. 
The Ampidex 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 inuch 
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 A'-ain, 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- 
closedfly always select the right end, 
and with what secretion is it sup- 
plied to decompose this mortar ?" 
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