106 THE AUSTRALIAN NATURALIST. 
Simuliidae (Buffalo Gnats); Fam. Tabanidae (‘Gad Flies,’** — 
“March Flies’’); Fam. Syrphidae (Hover Flies with rat- 
tailed larvae). 
Order Nezvuroprera.—Fam, Odonata 
about 120 species; Fam. Tricoptera (Caddis Flies); Fam. 
Sialidae (Alder Flies); Fam. Perlidae (Stone Flies); Fam. 
Ephemeridae (May-flies). 
Order Hemiprera (Bugs).—Fam. Hydrometridae (Fresh. 
and Salt Water Striders); Fam. Belostomidae (Large Water- 
Bugs); Fam. Notonectidae (Back Swimmers); Fam. Corixi- 
dae (Water Boatmen); Fam. Nepidae (Water Scorpions). 
Order LepipopTera.—Fam. Hydrocampidae (Moths with 
water weed caterpillars which breathe by gills). 
Order AptERA.—Podura spp. (minute leaping insects of 
surface of pools). 
We have also small grasshoppers and crickets which fre- 
quent marshes and edges of pools, and some semi-aquatic- 
beetles of the ocean beaches. In Europe a few species of 
parasitic Hymenoptera are known which swim through the. 
water, some with their legs, others with their wings, and lay 
their eggs in Dragon-fly eggs, Caddis-fly larvae, etc. 
Many of the oval-bodied carnivorous water beetles. 
(Dytiscidae) are plentiful in Sydney ponds and creeks, 
Sometimes, even in temporary rain-pools, they may be found 
disporting and frequently diving, some carrying an air bubble - 
at the tip of the abdomen. Diving is a particular habit, 
and Linnaeus, in recognition of this, called the first genus. 
Dytiscus, which means fond of diving. The adults fly at 
night, and a single night may people a pool with these beetles. 
They are voracious feeders on other water insects, larvae, 
tadpoles, and even small fish, and are dangerous in an aqua- 
rium where other small forms are being observed. A com- 
mon Sydney species is Rhuntus pulverosus, less than half an 
inch long; it is dark, smooth, and glossy. Our large species. 
is Cybister tripunctatus, which is a very deep green, almost 
black, and margined with a yellowish band. WHretes australis 
I have taken in bore water near Bourke, and it is probably 
one of the commonest species throughout western N.S.W. in 
ponds and bore tanks. It is a somewhat light brown species, 
about the size of /?. pulverosus. These Dytiscidae may live - 
as adults for a year or two, longer than usual with insects. 
They possess sharp biting jaws, and are direct cousins of the 
well-known land predaceous beetles (Carabidae) found com- 
monly under logs. All the time they are under water they 
have an excellent supply of air tucked away under the wing 
covers where the breathing spiracles open. To renew the- 
supply they need but swim, or float to the surface, for they 
are lighter than the water, expose the tip of the abdomen,. 
(Dragon-flies), 
