364 
Life-liistory of Melittobia acasta 
a normal phase in the life-history of the insect after she has exhausted her 
first supply of spermatozoa and preparatory to producing her second brood. 
It is mainly conjecture, but I believe that the female imprisoned in the host’s 
cell develops a desire to break out of the cell only when she has her sperma- 
tlieca full, so that once the female has produced her first brood she waits 
patiently for her second mating and then passes on to another cell to produce 
her second brood. My only evidence in support of this belief lies in the fact 
that in my glass cells the female was often to be seen on the cotton-wool plug 
after her second mating especially when the host larva within the cell was 
already fully stocked or was almost reduced to an empty skin. 
It is interesting to notice that inbreeding is the rule with this species, the 
first mating being between brother and sister and the subsequent ones between 
mother and son. Exceptions to this rule may occur when two females together 
enter a host cell and both produce a brood but as in such a case the two females 
must frequently come from the same cell, they will usually be sisters and the 
second mating would in this case be between nephew and aunt. 
I made a number of experiments with a view to seeing what an unfertilized 
female would do if I prevented her from mating by removing her eggs or 
larvae so that no male could develop, and these experiments have given 
somewhat interesting results. 
In the first place, as I have already mentioned, the life of the female is 
greatly prolonged, the ninety days, which I believe to be about the average 
life of the normal female, being, in a number of cases, more than doubled and 
in my eighteen experiments averaging 174-8 days. 
In the second place, whereas under normal conditions no imago is to be 
found after about the end of October, unfertilized females remained alive all 
through the winter, withstanding at times temperatures below freezing-point 
and only died in the second week of March after living 202 days—in fact, 
longer than many similar females kept at summer temperatures in the in¬ 
cubator. 
In the third place the female can be induced to lay many more male eggs 
under experimental conditions than she would probably do under natural 
ones—although it must be remembered that we have no definite knowledge 
of the number of male eggs laid by a female under natural conditions. 
Of eighteen cases, the average number of eggs laid per female was 35-6, 
one individual laying as many as 93 eggs, others 70 and 61, while one individual 
only laid 7 eggs in 131 days. In all these cases the experiment was kept going 
until the female died, so that the number of eggs obtained from each female 
was the total number she laid during her life. The following Table (III) gives 
the details of these experiments. 
