704 Marvels of the Universe 
the first cell is complete she seals it up and commences 
to build another immediately adjoining it ; sometimes 
the cells are made in a group, but more often they are 
placed in a line. With the closing of the cell the 
mother’s interest in her offspring ceases; she has done 
all that is needful for its welfare. The little wasp- 
grub emerges from the egg before many hours have 
elapsed, and quickly devours its provender. In eight 
or ten daysit has become a large, pale-coloured grub 
which occupies the whole of the cell. It then lies im- 
mured in the cell until the early months of the follow- 
ing spring, and in the meantime changes into the pupal 
stage. About the end of May it bites its way out and 
emerges as a pretty little black and yellow Wasp, 
pS . Tg ay aerate almost exactly like the parent Wasp that laboured so 
THE MASON-WASP. persistently on its behalf; the male Wasp, when he 
The insect, which belongs to the class of Solitary | emerges, may be distinguished by his much smaller size. 
Mae Sele Maem eames ies Such in brief is the life-story of this little Mason-Wasp 
shaped body and the two claws on the feet. when all has gone well ; sometimes, however, before the 
Wasp seals up her cell, she has a visitor—a most handsome, but, nevertheless, an uninvited guest. 
The lady on whose house the Mason-Wasp had built her nest-cells shown in the photographs, told 
me how she and her children had watched a ‘“‘ lovely green and red fly ”’ which sometimes came to 
the wasp-cells. [rom its description it was, doubtless, the Ruby-tailed Fly, which is like a 
gorgeously-attired house fly, its head and thorax, or middle portion, being of a vivid metallic 
green, while its abdomen glows with ruby fire. It should be observed, however, that it is a four- 
winged fly ; indeed, it is related to the wasps on which it preys. 
This insect will deposit its eggs in the cells of almost any wasp or bee to which it can gain 
access, and while the mother Wasp is searching for caterpillars, this parasitic visitor awaits 
its opportunity to enter her nest. Sometimes it is caught in the act, and attacked by the Wasp, 
when it immediately rolls itself into a ball and presents its glittering armour to the sting 
of its attacker, which in this case is 
useless. If it escapes unobserved, the 
mother Wasp carefully seals up the cell, 
enclosing the egg deposited by the fly. 
Then if, a little later on, the cell is opened, 
its larva will be found to have become 
full fed, but no trace will be found of the 
wasp-grub that should rightfully occupy 
the cell. It is highly probable that it 
would be the first and last meal of the 
parasitic grub, for its method is, I think, 
to emerge from the egg rather late, when 
the wasp-grub has finished its food 
supply, and then devour it. 
The same Mason-Wasp may _ have 
several “nests, the number of cells 
largely depending on the capacity of the CURIOUS HAILSTONES. 
site selected. Sometimes, too, this same 
Taken from a very early photographic print in the possession of 
species will build its nest in holes in sand- the Royal Meteorological Society. 
