134 
The South Australian Naturalist. 
eggs of a species (Cymathia americana) from Minnesota, and 
these are borne on long stalks just as are those of Porocorixa 
eurynome. 
At this stage is may be remarked that the following notes 
are the result of the activities of Mr. Fred. W. Shepherd, an en- 
thusiastic Naturalist; the writer here expresses his heartiest 
thanks to him. In April of this year Mr. Shepherd, in a letter, 
mentioned that some of the pools near Broken Hill, New South 
Wales, were then teeming with bug life, and that two species of 
backswimmers and a species of water-boatman were breeding in 
prodigous numbers in the Stephens Creek Dam. The reservoir 
paddock is about fourteen miles in circumference, and is situated 
some miles out from Broken Hill. At the writer’s request Mr. 
Shepherd covered the distance to the breeding pool on several 
occasions for the taking of notes and material. 
On the western side the dam Is Intermittently fed by Stephens 
Creek; deep water occurs only at the eastern end near the pump- 
ing station, and the greater part of the water is shallow. In this 
shallow area eggs of the bugs were attached to stones and rub- 
bish literally in millions, and later, as the young bugs passed 
through their nymphal stages, the receding water and lap of 
wavelets deposited rills of moulted skins on the mud. Towards 
the end of autumn the whole north-western side was bordered 
with from nine to twelve of these rills, each about nine inches in 
width, while in the water was a ten-inch margin of floating and 
submerged skins. The water was turgid, with a stinking black 
mud bottom; no large aquatic plants were present. A sample of 
material sent down for examination was remarkably foul, although 
passed through two changes of clean water before despatch. The 
mass consisted largely of Spirogyra and a very fine branched alga; 
these algae were devoid of chlorophyll and almost every thread 
of vegetation had eggs fastened to it. A quantity of the bugs and 
some stones with eggs attached were also forwarded to Adelaide; 
the water-boatman was another species of Porocorixa (P. hirti- 
frons) and the eggs obviously belong to this species. They are 
similar to those of P, eurynome, but differ in having uniformly 
shorter stalks and larger pads of attachment (cf. text fig. 1, c and 
d); the two bottom figures show how the apex of an egg is split 
as the nymph emerges. A test showed that, just as with the 
ova of P. eurynome, the stalks are elastic and, if stretched, spring 
quickly back when released. Also that if a continued pull is 
given, the pad of attachment leaves its support, but the connect- 
ing thread rarely breaks. The photograph shows how closely 
the ova are arranged on the stbnes; excepting where smaller 
pebbles and rubbish have been overlying it the whole surface Is 
occupied by the eggs, indeed so crowded are they that the out- 
