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Twelve to fifteen are usually laid at one time on submerged objects, G. subsłriałus Steph. and G. łhomsoni Zaitz., in captivity, usually deposit their eggs in short rows end to end, on the walls of the aąuarium, It has also been recorded that they oviposit on roots, rotting leaves, and other dead vegetable matter. It is usually stated that they deposit their eggs on emergent vege-tation a little below the surface of the water. Probably they normally oviposit on any submerged object, of sufficient stability, irrespective of its naturę. Egg laying commences in early Spring, several batches of eggs being laid over a period of some weeks.

The time taken for development varies in different species and in relation to temperaturę to an even greater extent. Under the usual conditions existing in North Europę the time taken for the development of the ova of G. subsiriatus is said to be about 14 days.

The larva is elongated with a smali head and thorax and a long and swollen abdomen. The head is flattened and bears a pair of sharp pointed, tubular, sickle shaped mandibles, simi-lar to those of a dytiscid larva. They are directed upwards so that they may, when very tightly closed, come to lie with the tips above the front of the head. The larva appears to feed in the same way as a dytiscid larva: the prey is piercod by the sharp points of the mandibles, a digestive secretion is then pumped into its body, the secretion paralizes rapidly and then kills and liquefies the tissues, finally the pumping action of the pharynx is reverscd and the liquid contents of the victim is sucked through the mandibles. The process is rapid and efficient. The whole of the nutritive matter is removed and the digestive system is not burdened with the presence of chitin and other indigestible matter or with excess of water.

Respiration is effected by means of ten pairs of long plu-

mose

tracheal gills, The first eight abdominal segments each

bear one pair of these respiratory outgrowths and the ninth segment bears two pairs. The larvae are thus free from the need to obtain atmospheric oxygen and can penetrate to consi-

derable depths. This is unusual in the 1arvae of Coleopłera.

The head and first thoracic segment are well c

ise

d

but the second and third thoracic sctfments and abdomen are soft. The legs are slender. The extremity of the abdomen bears