What a day with Chironomidae
I chose the family Chironomidae as my insect group because I
have had many previous experiences and research with this group,
especially within the last 4 months. In this blog post, I would like to first
take you through a portion of one of my sampling days and then give more
details about this family. Imagine a cold April morning, the sun is covered by
clouds, and it has been raining heavily for multiple days. My research partner,
professor, and I have just exited the van after driving over 2 hours to get to
our first site for the day. The rain has momentarily stopped, and we are ready
to search for midges; these prized larval flies are all we are sampling for,
but with the heavy rains, the stream is very high and moving quickly. As we wade into the water, my research partner
begins the substrate pick sampling while I, equipped with chest waders and a
D-shaped net, search for a riffle to begin the multi-habitat substrate kick
sampling (kicking). With the high flow, it's very difficult to find a riffle,
so I settle for a spot underneath the overpass we used for entry. My second step
drops me into the water with the level about halfway up my torso. As I trudge
against the flow, I reach my spot, and because the flow is so high, I struggle
to get my sweeping kick momentum going. As I am trying to kick substrate into
the net, I stumble, and water partially fills my left leg. However, it was worth it
because my kicking in that particular stream yielded four midges (like the ones
pictured below). Was I supposed to get 30? Yes.
The family Chironomidae, or non-biting midges, are among the
true flies, or order Diptera. They are most frequent and abundant in freshwater
habitats (lotic or lentic), but some brackish species occur. Chironomids are
geographically very widely distributed, with family members on all continents.
This wide distribution is linked to their tolerance of extreme environmental
conditions (e.g., pH, depth, current velocity, hypoxia) and negative
anthropogenic effects (e.g., pollution). Chironomidae’s large distribution and
tolerance to a wide variety of harsh conditions make them an ideal indicator
species for freshwater system health. This is because the dominant presence of Chironomids
as opposed to more sensitive taxa like Ephemeroptera, Plecoptera, and Tricoptera
can be a result of a degraded stream. Chironomid larvae are often referred to
as bloodworms, partially for their worm-like appearance. They also have paired
prolegs on the prothoracic and last abdominal segments. Adult midges have
slender legs, narrow, scaleless wings, and males have plumose antennae (see
picture below). They are often misidentified as adult mosquitoes; however, they
do not have the long proboscis that mosquitoes do and cannot feed on blood. There
are estimated to be up to 15,000 species of these midges worldwide (It should
be noted that this estimation is considered high and should be viewed
skeptically).
An Adult Male Chironomid
Although there are considerable amounts of research and
information about chironomids as bioindicators for aquatic environments
worldwide, studies about these insects and their environment are still scarce.
The hardest aspect of studying Chironomidae is their small larval size and
challenging taxonomy. Which is usually distinguishable only by mouthparts (see
figure below). However, proper identification, especially at the species level,
would greatly improve the effectiveness of biomonitoring efforts. Midges are
also important in trophic dynamics as their relative abundance is an important
food source for predators, such as fish and birds. Certain Chironomid taxa also
recycle detritus, returning nutrients to the upper trophic level when the
midges are consumed.
Eukiefferiella devonica grp. mouthparts under a
microscope
References
https://content.ces.ncsu.edu/biology-and-control-of-non-biting-aquatic-midges
https://resjournals.onlinelibrary.wiley.com/doi/full/10.1111/icad.12123
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