819 AUSTRALIAN MEGALOPTERA OR ALDER-FLIES, With Descriptions of new Genera and Species. By R. J. TiLLYARD, M.A., D.Sc, F.L.S., F.E.S., Linnean Macleay Fellow of the Society in Zoology. (With three Text-figures.) The Megaloptera are an archaic Order of Holometabolous Insects, which contains, at the present day, only about one hundred known species, all of them of large or moderate size. The Order is divisible into two very distinct Sub orders, viz., the Sialoidea, or true Alder-flies, and the Raphidioidea, or Snake-flies. Of these, the aquatic Sialoidea are clearly the more archaic, the terrestrial Raphidioidea being a highly specialised offshoot from them. The Raphidioidea are not represented in Australia, their place in the economy of Nature being already occupied by the older Fsychopsidm of the Order Planipennia. whose larvae, though differing in the nature of their mouth-parts, live, like those of the Snake-flies, in crevices of the bark of trees, and prey upon the insects frequenting them. The Sialoidea, or true Alder-flies, are represented by some sixty species throughout the world. They may conveniently be divided into two very distinct families, according to the follow-ing key :— 'Large insects (expaii.se -loto 100 mm. ^, with three ocelli present; fourth joint of tarsus not bilobed; venation regular, with cross-veins weakly formed, Larvfe with eight pairs of lateral gills and a pair of hooked anal prolegs, but without any ter-minal filament CORYDALID.^;. Much smaller insects (expanse 20 to 40 mm.), without ocelli; fourth joint of tarsus strongly bilobed; venation less regular, Avith strongly developed cross-veins. Larvie with only seven pairs of lateral gills and a terminal filament, but without any anal prolegs . . Sialid.i;.