F. B. Browne 
363 
IX. Longevity of the Female. 
Table I, already referred to, shows that, in the cases of the four females 
which produced second broods, the length of life varied from twelve to sixteen 
weeks, i.e. 84 to 112 days, and that, during all this time, they were actively 
ovipositing. Graham Smith (1918-19) records having seen one female ovi¬ 
positing over a period of 48 days and another over a period of 37 days but it 
is possible that his observations were upon females which had no chance of 
a second mating and had therefore ceased to lay eggs because they had 
exhausted their supplies of spermatozoa. 
I have several other records of ovipositing females which survived for 
periods exceeding 90 days and it seems, therefore, that, under normal con¬ 
ditions, this would be about the average length of life of the female. 
If, however, unfertilized females are prevented from mating, the length 
of life is enormously increased, eight such females having lived as follows: 
211, 204, 225, 223, 209, 195, 202, 202 days. This will be referred to further 
in the next chapter where full details are given in Table III, p. 365. 
X. The Unfertilized Female. 
I have already mentioned that, under natural conditions, the males never 
leave their natal cells, so that mating takes place there: and I believe that it 
is not until after mating has taken place that the females become positively 
heliotropic. I have never, under natural conditions, come across an unfertilized 
female; that is, every female which has been allowed to emerge from the pupal 
stage in the cell where it grew up mates before leaving that cell. It is 
quite easy, however, to obtain unfertilized females by simply removing female 
pupae from the cells and allowing them to hatch out without a male having 
access to them. 
Several authors mention the results of experiments with unfertilized 
females. Such a female, when placed in a cell with suitable food material 
will, sooner or later, lay a small number of eggs—it may be only one but is 
more usually four or six, though occasionally there are a few more. The female 
takes great interest in these eggs and in the larvae which hatch from them, 
patting them with her antennae and returning to them again and again. She 
takes, perhaps, greater interest in the resulting pupae and may even be said 
to show excitement when one of them is about to become an imago. All the 
resulting imagines are males and she mates with the first one to emerge and 
within a very short time commences to lay freely, twenty or thirty eggs some¬ 
times being deposited within twenty-four hours of the appearance of the 
male. 
At first sight this habit of the unfertilized female of producing her own 
mate when another is unobtainable seems a somewhat extraordinary phe¬ 
nomenon and yet, from what I have shown by experiment, it appears to be 
