208 THE AUSTRALIAN NATURALIST. 
around the body and between the wings. Such a habit 
might perhaps be explained as an attempt to have the eggs 
immersed in water, even should the water evaporate and the 
surface sink several inches; or, is it to escape parasites or 
predaceous enemies of the air? It is of interest to note that 
‘several minute parasitic wasps, however, descend into the 
water and lay their eggs within dragon-fly eggs in the weeds. 
Such aquatic parasitic species have not been recorded from 
Australia, but investigation may yet show their presence. 
We cannot enlarge here upon the interesting habits of 
Dragon-fly larvae, or nymphs as they are called. They pos- 
‘sess a hinged under lip capable of sudden extension to grasp 
living prey. They breathe by gill plates at the tip of the 
abdomen as in Lestes, or the gill plates are absent and water 
is taken into the rectum, and there the blood is aerated in 
special folds of the rectum. And this water may be ejected 
from ‘the rectum with such force as to, drive the larvae for- 
ward with a darting movement. Altogether these nymphs 
form most interesting aquarium specimens. They live per- 
haps two seasons in many cases, and are to be obtained plenti- 
fully in the mud and weeds of our pools, even in midwinter. 
Our largest Sydney Dragon-fly is Petalura gigantea, 
about 43 inches across the wings, but the largest Australian 
species, and perhaps in the world, is Petalura ingentissima, 
a species recorded from Queensland by Mr. Tillyard, and 
which is over 6 inches across the outspread wings. The genus 
Petalura presents an addition to the unique types of the 
Australian fauna, and the abdominal appendages of the male 
and other features, as Mr. Tillyard has pointed out, indicate 
that they are primitive forms structurally. 
Of other groups it may be mentioned we have, as indi- 
cated in the list, Stone-flies, May-fiies, Caddis-flies, etc., 
which all have aquatic larvae, but scarcely any of our forms 
are known to science. These larvae are favourite food of tha 
freshwater fish, and anglers the world over use them for bait, 
and, incidentally, hosts of local names for these aquatic 
larvae have arisen. Of two-winged flies with aquatic larvae 
there are small, slender crimson larvae known as blood worms, 
commonly found in the mud scooped from the bottom of our 
pools. These are the larvae of Chironomus (Midges). They 
form a: favourite food for freshwater fish. Examination in 
lakes and ponds in New York State and Yellowstone Park, 
U.S.A., showed that 50 ner cent. of the diet of certain brook 
trout consisted of these blood worms. Allied to Chironomus 
is the genus Ueratopoyon, to which our Sydney Sand-flies, 
Ceratopogon molestes, Skuse, belong. Some species, of the 
genus have aquatic larvae, but the larvae of many live in 
‘damp places, wet soil or bark, liquid gum of ‘trees, etc. 
