VICTORIAN SPECIES OF CHIMARRA 
21 
Based on instars 3-5 only, numbers of C. mon- 
ticola in the Yarra River were typically low (less 
than 10% of the Chimarra individuals in each 
sample collected during 1979-80), although in 
samples collected in August and October of 
1978, C. monticola comprised 29% and 25% of 
the total Chimarra numbers respectively. 
Size distributions of instars of C australica in 
the Yarra River samples during 1979-80 are 
illustrated in Fig. 22. The life cycle is difficult to 
interpret due to the absence of samples in some 
months, and the wide range of instars at certain 
times of the year. Instar 1 and 2 larvae were col¬ 
lected in April and May of 1979, and probably 
overwintered mainly as instars 3-5 and pupated 
during October-November. Instars 1 and 2 
appeared in samples again in December and 
January, and probably grew rapidly to pupate in 
late summer-early autumn. Pupae were col¬ 
lected in February, April and October. With 
early instars present in autumn and summer, 
and pupae in late spring and late summer- 
autumn, the life cycle appears to be bivoltine, 
although poorly synchronized. 
Capture nets of C. australica final instar lar¬ 
vae from the Yarra River had mesh openings of 
1.1-1.2 pm by 2.1-14.6 pm. C. monticola in the 
O’Shannassy River had capture nets with mesh 
openings of 0.9-1.2 pm by 5.5-18.0 pm. 
DISCUSSION 
The two Victorian species of Chimarra can be 
distinguished by small but reliable characters: 
the shape of the anterior margin of the frontocly- 
peus and mandibles in final instar larvae; the 
number of teeth on the abdominal hook plates in 
pupae; and the shape of the distal sclerites 
attached to the ninth abdominal stemite of 
females. The shapes of both the frontoclypeal 
notch and the mesal margin of the mandibles 
have previously been used to distinguish larvae 
of Chimarra species in North America (Ross 
1944) and South America (Marlier 1964). In 
pupae, there is some variability in the number of 
teeth on the hook plates of most segments, and 
this variability has also been reported by Lep- 
neva (1970). This character should be used with 
some caution, although it has been found re¬ 
liable in material examined in the present 
study. 
The life cycle of C. australica in the Yarra 
River is poorly synchronized and apparently 
bivoltine. This contrasts with the life cycle of C. 
monticola, which was reported by Dean & 
Cartwright (1987) to be well synchronized and 
univoltine. These differences can be explained 
by the higher water temperatures recorded in the 
Yarra River. Similar differences have been 
reported from the northern hemisphere, with 
bivoltinism being reported in species of Chi¬ 
marra in Georgia (USA) by Cudney & Wallace 
(1980), in Virginia by Parker & Voshell (1982), 
in Quebec by Morin & Harper (1986), and in 
South Carolina by Smock (1988). Univoltinism 
has been documented in C. atterrima Hagen in 
Illinois by Ross (1944) and in Ontario by 
Williams & Hynes (1973). 
Although C. australica was always dominant 
in the Yarra River during the study period, the 
proportion of C. monticola was higher in August 
and October of 1978 (25-30% of Chimarra 
individuals collected) than in 1979 (less than 
10% of Chimarra in each sample). The higher 
proportion of C. monticola in 1978 may have 
been related to the much higher water flow in 
that year. 
Nets of Chimarra species have been little 
studied. Wallace & Malas (1976) found that final 
instar larvae of C. socia? in North America pro¬ 
duce nets with mesh openings ranging from 0.8 x 
3 to 0.8 x 9 pm. In comparison with these sizes, 
the mesh openings of final instar larvae of the 
two Victorian species were slightly greater in 
width and extremely variable in length. 
ACKNOWLEDGEMENTS 
I am extremely grateful to Alice Wells and John 
Dean for their encouragement and constructive 
comments during the preparation of this man¬ 
uscript. I also thank Arturs Neboiss for com¬ 
ments on an earlier draft of the paper and for 
making available adult material in the collec¬ 
tions of the Museum of Victoria, Melbourne. 
REFERENCES 
Barnard, K. H., 1934. South African caddis-flies 
(Trichoptera). Transactions of the Royal Society 
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Cartwright, D. I. & Dean, J. C, 1982. A key to the 
Victorian genera of free-living and retreat¬ 
making caddis-fly larvae (Insecta: Trichoptera). 
Memoirs of the National Museum of Victoria 
43: 1-13. ' 
Chessman, B. C, 1986. Dietary studies of aquatic 
insects from two Victorian rivers. Australian 
Journal of Marine and Freshwater Research 37: 
129-146. 
Cudney, M. D. & Wallace, J. B., 1980. Life cycles, 
microdistribution and production dynamics of 
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