354 
Life-history of Melittobia acasta 
But females can delay oviposition apparently almost indefinitely, even 
when their abdomens are swelled almost to bursting point, if the host is not 
in a suitable condition or, as will be seen later, if mating has not taken place. 
Thus I have had females laying within 24 hours of emerging from the pupal 
stage, when placed upon suitable material, and I have had other females which 
had not oviposited 50 and even 60 days after emergence, when placed in a 
cell with an unhatched egg of the host-species, these females having waited 
for the host to reach the full grown larval condition before commencing 
oviposition. 
(b) The egg. (Plate XXVI, fig. 5.) 
The eggs, which are hyaline and almost transparent, vary somewhat in 
shape and in size. The smallest eggs measured were about *33 mm. in length 
while the largest were about -37 mm. They are elongated and taper somewhat 
towards one pole and measure about -1 mm. across at the widest part. Some 
taper more strongly than others and as these were scarcer I assumed at first 
that they were destined to produce males, but experiment showed that this 
was not the case and that there is no visible difference between male and 
female eggs. 
The egg is not firmly fastened to the host but adheres very slightly as if 
it were just damp. It is quite easily lifted off by means of a needle point or 
fine brush but as a rule it will not fall off if the host is turned over. If, however, 
in the process of turning over the host, the egg comes in contact with the 
glass cell it adheres more readily to the latter. 
Incubation varies from 2 to 9 days and the emergence of the larva from 
the egg is almost impossible to determine. The chorion is extremely thin and 
the larva apparently begins to feed through it, as I have observed is the case 
in some other hymenoptera, for instance Trypoxylon figulus. Sooner or later 
this thin "shell” splits and contracts. 
(c) The larva. (Plate XXVI, figs. 6 and 7.) 
The newly emerged larva is transparent and is composed of a head and 
thirteen segments. The tracheal system shows only four pairs of spiracles, one 
on the mesothorax and one on each of the first three abdominal segments, 
though the branches from the lateral trunks in the three or four succeeding 
abdominal segments indicate where, at a later stage, additional spiracles will 
appear. 
The larva remains in the first stage from two to six days or even longer 
and then a moult takes place and five additional pairs of spiracles appear, 
one on the metathorax and the others on the fourth to the seventh abdominal 
segments. I have never actually seen a moult take place but, by examining 
numbers of larvae -60 to -70 mm. in length, it is possible to find individuals 
about to moult in which the additional spiracles are faintly visible sub¬ 
cutaneously. 
