19 
THE PUPATION OF A WATER BEETLE. 
LLEWELLYN LLOYD. 
FEw insects are more frequently kept by the amateur naturalist 
in his aquarium than the Dytiscus larva. Its rapacious 
appetite and robust health in captivity make it a most interest- 
ing pet, and one species, Dytiscus marginalis, is easily procurable 
in various stages throughout the summer in most of the ponds 
of Yorkshire. As a rule, the insect dies in captivity, without 
undergoing its metamorphosis, but if it is properly treated, 
all its stages may be readily observed. 
It requires a plentiful supply of food, such as tadpoles or 
small fishes, but the writer has reared his specimens almost 
entirely on centipedes and earthworms. One instance of its 
rapacious habits may be cited: a specimen almost mature 
was placed in a small vessel with eighteen large frog tadpoles 
and two sticklebacks. In twenty-four hours it had destroyed 
them all. 
-When the larva is about two and a half inches in length, 
and has commenced to refuse food actually placed within its 
jaws, it should be removed from the aquarium, and given an 
opportunity to burrow. The following method has been used, 
and has met with considerable success. A round shallow 
pot was filled with moss and water to the brim, and the larva 
was placed in it with a supply of food in case it required another 
meal. The vessel was then placed in a plant pot nearly full 
of moist soil, and was pressed in until the earth was level with 
itsedge. The plant pot should be covered to prevent the insect 
escaping, as it is now ina peripatetic mood. It soon leaves the 
water, and wanders about looking for a suitable place in which 
to burrow. The burrowing is done mainly with the legs, but 
the flat head is used as a shovel, throwing the earth backwards 
between the legs. The burrow is only about an inch in depth 
and at the bottom a flat oval chamber is formed. 
By a simple device the formation of the chamber may be 
observed. The surface of the soil is made very firm by pressure, 
and a hole is made with the finger at the side of the vessel 
containing the grub. The hole should pass close to the vessel 
and to some extent underneath it. In the writer’s experience, 
the larva has always taken advantage of such a hole. If the 
vessel is now carefully lifted out of the soil,a good view of the 
little workman may be obtained as often as desirable. The 
grub at its work is a most decrepit object, its back and head are 
caked with mud, its antenne and palpi are draggled, and its 
anal cerci are no longer turned upwards as in life, but down- 
wards, so as to keep the soil out of the stigmata. The white 
colour of the pupa is seen through the skin, and a couple of 
1gi1 Jan. 1. 
