Illinois Natural History Survey Reports

              Monitoring of the entire aquat-ic
invertebrate community has
been an effective tool for docu-menting
changes in stream health.
Recent studies suggest that a
subset of sensitive aquatic insects
may actually provide information
more quickly (and cheaply) than
the entire community. The EPT
index (number of Ephemeroptera,
Plecoptera, and Trichoptera spe-cies
in a sample) is one of the
most efficient indices of stream
health due to its ease of use and
low variability. Its usefulness in
monitoring stressed ecosystems
has been tested by the addition of
insecticides to experimental and
control watersheds in the North
Carolina Piedmont. Researchers
found that EPT values in samples
dis-played
low
vari-ability,
showed
dif-ferent
effects
in dif-ferent
stream
habitats
(leaf
packs,
moss,
sand
bot-toms),
and cor-related
well with other more costly mea-sures
of ecosystem function such
as rates of nutrient processing,
total invertebrate diversity and
biomass, and with the calculation
of a biotic index specific to the
region.
The Illinois Natural His-tory
Survey has been a hotbed
of research in the taxonomy,
distribution, and ecology of may-flies,
stoneflies, and caddisflies
throughout the century. Survey
entomologists including Barnard
D. Burks (mayflies), Theodore H.
Frison (stoneflies), and Herbert
H. Ross (caddisflies) wrote a
large proportion of the original
descriptions for North Ameri-can
species during the early and
middle part of this century. The
ILLINOIS
NATURAL
HISTORY
S URVEY R e p o r t s
November/
December 1997
No. 348
I N S I D E
Continued on back page
Summertime evening strolls
along the banks of Illinois rivers
and streams provide an opportu-nity
for Illinoisans to encounter
aquatic insect adults. The adults
of mayflies (Ephemeroptera)
and caddisflies (Trichoptera) are
the most frequently encountered
groups, but the lucky observer
may find the more ecologically
sensitive stonefly (Plecoptera).
Fishermen know these insect or-ders
as the “hatch to match” when
choosing or making artificial
“flies” to catch a trout or other
gamefish. The immatures of
these insects live inconspicuously
in gravel, on logs, and buried in
the mud of large rivers, streams,
and lakes. The life cycles of
some species last for only sev-eral
months, but other species
must live in the stream for up to
several years before changing to
the winged adult stage. It is the
immature stages of these insects
that aquatic biologists use to
monitor changes in water quality
of streams.
Mayflies, Stoneflies, and Caddisflies Help
Researchers Track Water Quality
Stonefly larva in stream substrate.
Mayfly
larva.
Photo by Denise Stoeckel, INHS
Center for Aquatic Ecology
Photo by Michael Jeffords, INHS Center for
Economic Entomology
Photo by Denise Stoeckel, INHS Center for
Aquatic Ecology Cowbird Parasitism in
Different Habitats
2
New Publications
3
Hydroacoustics: A Tool
for Understanding
Fish-Habitat Associa-tions
in Rivers
4
Gypsy Moth in the
Chicago Area: Disaster
for All or Moderate
Problem for Some?
5
Species Spotlight:
The Sycamore
6
The Naturalist's
Apprentice:
Big Trees!
7
Caddisfly larva.