30 Mr. F. Merrifield's Practical suggestions and 



and provision may be made for occasional cross-breeding 

 to promote the vigour of the breed. Observers living in 

 countries where there is a large choice of double-brooded 

 insects, especially where the climate is such as to admit 

 of three or four broods a year, have great advantages. 

 Under such conditions probably some of the silk- 

 producing Bombyces would be favourable subjects. 



Apart from the bearing of the experiments on the 

 theory of heredity to be elucidated, they can hardly fail 

 to throw light on many problems in evolution, such as 

 those which have been investigated by Prof. Weismann, 

 as well as to furnish facts of interest in the life-history 

 of the insects chosen for experiment ; — such as the 

 proportion of males and females, and the order in which 

 they appear ; the time of the day or night when they 

 emerge from pupa ; the time when they are most active 

 on the wing, or in feeding as larvae ; the number of eggs 

 laid ; the duration of life in the several stages ; the 

 influence of temperature, moisture, and food-plant, &c. ; 

 — facts many of which have a general interest for 

 entomologists, but which are rarely recorded with 

 completeness and accuracy by those who only breed for 

 cabinet purposes. 



Attention is called to the importance, whatever species 

 is chosen, of starting with a healthy original stock. 

 Pupse freshly dug or obtained from larvae found wild, or 

 eggs from moths caught wild, are preferable, as there 

 need be no apprehension that they are suffering under 

 defects engendered by feeding under artificial conditions 

 or by interbreeding. In any case the origin or history 

 of the stock with which the experiments are begun 

 should be known. A supply from a foreign country 

 does not appear to be objectionable, if the species 

 obtained there is known to have the ordinary appear- 

 ance, size, and habits of the native specimens. 



The writer will be greatly obliged to any entomologist, 

 having had practical experience in the rearing of larvae, 

 for any suggestions tending to ensure success in the 

 experiments determined on. He would be particularly 

 obliged by answers to the following enquiries : — How 

 long can such moths as the Selenias, spring and summer 

 broods respectively, be kept alive and quiet, and how 

 can this best be done ? Can any better plan be suggested 

 than that of subjecting them to cold and darkness, and 



