416 Dr. Wallace on the Oak-feeding 
voraciously for three or four days, during which time abundance 
of food must be supplied. If they eat their old skin it is a sign 
that fresh and proper food is not supplied to them. In the last 
stage the worms require well-developed leaves. Young green 
shoots are to be withheld as injurious, being too watery. Care 
must be taken, when the worms are looking out for a site for their 
cocoons, not to disturb them by changing the food. If once dis- 
turbed they rarely spin again and change into pupa. Fresh 
branches therefore, if required, must be placed on the outsides for 
those worms which are still eating. If there is one worm still spin- 
ning, and another commences to eat the leaves which envelope the 
cocoon, the first is often disturbed and falls, and frequently dies, 
as a slight blow proves fatal at that period. At spinning time 
the waterpot is to be withbeld.* Fifteen or twenty days after the 
cocoons are begun they may be cut off, and a thread or string be 
passed through the upper portion, above where the moth emerges, 
so that the pupa hangs vertically. ‘They are then to be hung up, 
ten atatime. If, however, the cocoons are not all spun at the 
same time, this cannot be done to a nicety ; and then, as the change 
into pupa has not taken place, great care must be taken in gather- 
ing them to avoid shock or pressure; in order to preserve these in 
a vertical position they may be suspended by a hook for a few 
more days, and afterwards treated as the others. 
The cocoons may now be divested of their dried leaves and 
wound, if desired ; but if reserved for breeding, further care is 
necessary. Naturally the males would emerge first, the females 
later, and in order to obviate this and obtain both males and 
females at the same time, it becomes necessary to hasten the exit 
of the latter and retard that of the males. It is necessary also 
to hasten the last formed cocoons, and retard the earlier ones, in 
order that the moths may all emerge about the same period, which 
would give a better chance of obtaining eggs with a minimum of 
uncertainty and trouble. 
In a state of nature the exit of insects is prolonged often over 
a considerable period, doubtless in order that a greater chance may 
thereby be given for continuing the race. For were it otherwise, 
and the majority of one species were hatched out simultaneously, 
a fortuitous coincidence of unfavourable conditions, atmospheric 
or otherwise —as, for instance, a sudden frost or inundation—might 
* The change into pupa being about the seventeenth to nineteenth day 
after beginning to spin; vide Revue de Sériciculture, 1865, p. 76. 
