In the genus _Gerris_, Skuse (Records of the Australian Museum, 1893) described a species from the waters of Sydney Harbour under the name of _Gerris australis_. It varies from dark shining olive to black on the dorsal surface; the ventral surface is yellow with grey tints. It is covered with a fine silvery pubescence, and measures ⅓ of an inch in length. _Hydrometra strigosa_, described by Skuse from specimens from the swamps about Botany, N.S.W., is a larger insect, of a uniform brownish yellow tint; and it has a more slender shape. _Halobates whiteleggi_ is a small ochreous water-bug about ⅙ of an inch in length, and was obtained by Skuse in swarms in the sheltered nooks of Sydney Harbour. Another species discovered in Torres Straits has been named _Hermatabates haddeni_, after its discoverer, Professor Hadden. The closely allied small family HENICOCEPHALIDAE consists of a single genus, the members of which are widely distributed. We have one described from Tasmania by Westwood under the name of _Henicocephalus tasmanicus_. They fly in swarms, dancing in the air together like midges. It is noticed they give off a musk-like smell. Family 8. Assassin Bugs. REDUVIIDAE. This is a large division of the Hemiptera, and its members are carnivorous, destroying different kinds of insects, which they impale with their beaks, and from which they suck the blood; many can give a painful stab with the stout beak if handled carelessly. The head is long, narrowed behind, and freely movable; the rostrum or beak is short, stout, and is curved under the head, not extending far under the thorax; the antennae are long, slender towards the tips; the legs are long, slender, and often hairy; the elytron consists of three divisions. Some species are wingless. They exhibit much variety in size and colouration, and their shape is often adapted to their habits. The large immature forms of one undetermined species, found plentifully about Maitland, N.S.W., hides in the sand under the shelter of a log or stone; each covers its back with bits of sand or dirt, and, thus disguised, it lies in wait for its prey. Over 2,000 species are described from all parts of the world, and they are grouped into 14 sub-families. The EMESINAE contain a very curious group of slender grey bugs with long legs. They might at first sight be mistaken for “daddy longlegs” or “crane-flies”; and are found, too, in similar situations, viz., resting on tree trunks or under the cover of logs and bark; and they probably live chiefly on these long-legged flies. _Gardena australis_ is of a uniform brown tint, mottled on the legs and elytra with grey. It is of the usual slender form, with elongate hairy legs. It and several similar but undetermined species are common about Sydney.