The Caddisfly is one of many species of flies that find their habitat around water. A single Caddisfly is a bionomic body - a body that speaks to its relations with its environment and other species. While the scope of their depletion is difficult to determine, we know that their ties to the ecosystems that sustain them can offer us insight into the ecological impact of human life. Their life cycle illustrates this.

At the beginning of their lives, in the larval stage, Caddisflies construct cocoons on the riverbed. To begin the home-making process, they chew on surrounding substances such as pebbles, leaves and twigs into functional cocoon-building materials. Caddisflies have always used the organic materials available to them, but recent laboratory experiments have shown that they will readily incorporate inorganic materials such as plastics into their homes. These microplastics accumulate in the Caddisfly’s body, which then circulates in the food chain. As these inorganic materials are digested by the Caddisfly and again by other organisms, they are broken down into ever smaller particles. In addition to breaking down larger particles, Caddisflies retain organic matter through their capture and packaging work. Consequently, the biological cycle of Caddisflies plays a role in the circulation of microplastics.

Incorporated plastics appear to be one of the reasons for the decreasing Caddisfly population since the inorganic materials deteriorate their shelters, but the interrelatedness of ecosystem demands that we need Caddisflies - the Caddisfly not only reworks the soil by scraping the riverbed, but also pumps nitrogen into the environment. Rivers polluted by man - by Thames Water - drive this cycle of sabotage.

Biosensor, indicator species, bionomic body: the riverfly is a canary in the coalmine, connected with a number of salient ecological bodies and therefore particularly sensitive to changes in the environment. It engages with terrestrial and aquatic landscapes, moving between the two to breed, build a home and feed. It serves many functions in its ecosystem along the way, but these tend to go unnoticed. Meanwhile, the raw sewage discharged into the ecosystems have an outsized impact on the riverfly, affecting it before its polluting effects ever get to us.

Raw sewage spills trigger a causal chain for the riverfly and its environment. Untreated sewage is rich in nitrogen and phosphorus. Both chemical elements create an environment for phytoplankton or mats that lead to algal bloom. Algae, flourishing on the surface of water, block sunlight which plants need for photosynthesis. Dead plants and algae are eaten by bacteria, reducing the oxygen level in the water. Sewage fungus, a mutant amalgamation of various types of bacteria, also thrives in the reduced dissolved-oxygen environment of these rivers, and their presence in an ecosystem can lead to ecosystem breakdown: smothering fish eggs, severely depleting oxygen levels, and causing unpleasant smells.

High levels of phosphorus are especially dangerous for chalk streams, million-year-old rivers that are fed by chalk aquifers. The clarity and its stable flow makes them a unique and essential part of a rich ecology and an important habitat for many different species, including riverflies. As the heatmap suggests, a high number of indications of pollution affecting riverfly populations were found in areas of chalk streams. With the decrease of riverflies, predators, such as wild fish, birds and mammals, lose an important food source, which severely impacts other wildlife populations. There are 260 chalk streams in the world, 85% of which are located in Southern and Eastern England.

The chemical and material disturbances of water bodies became a catalyst of a whole new agency of "Citizen Scientists", a constantly evolving group of actors that monitor the riverfly and the health of our environment, forming a human-animal alliance.

Long before the establishment of riverfly monitoring, local communities began observing changes in riverfly habitats. The Riverfly Partnership, a citizen science monitoring scheme supported by the Freshwater Biological Association (FBA) and Environment Agency (EA), provides standardised monitoring practices and technical instruments to assess river health. Besides initiating the pioneering Anglers’ Riverfly Monitoring Initiative (ARMI), the Riverfly Partnership also launched the publicly accessible ARMI database and Riverfly Census report which provides scientifically in-depth data, as well as two other schemes: The Urban Riverfly Scheme, an alternative to ARMI which focuses on urban areas with low scoring river condition, and the Extended Riverfly Scheme, which introduced an additional 33 groups of freshwater macroinvertebrates to provide extended biotic indices on river sites at milder levels of stress.

The ARMI procedure is a simplified biomonitoring method that involves collecting standardised 3-minute kick samples of freshwater invertebrates from a river site, followed by a sampling inspection of a nearby large stone where macroinvertebrates can be found. An ARMI score is then generated to reflect the river condition. A trigger level score is also registered in each sampling site. If the level is shown to be significantly low on the long-term data, local regulatory authorities will be notified and agency officers will conduct investigation and corresponding implementation.

Despite concerns towards the accuracy and viability of citizen science, the results achieved by ARMI and the regulatory authority, Biological Monitoring Working Party (BMWP), are almost identical. Monthly monitoring by ARMI volunteers also identified various pollution incidents which were previously unknown to the EA. For example, the phosphate contamination from the tertiary sewage treatment in River Kennet in July 2013, discharges into the River Derwent in November 2009, and River Bulbourne between October 2015 and April 2016.

The fly’s position - as a small and ubiquitous being - offers us an important perspectival shift that puts into question the various human fantasies that begin to come undone under, for instance, a closer look at the practice of sewage and water treatment. As the theorist Donna Haraway would put it, the fly’s perspective becomes an important situated knowledge which enables us to better address the many agents at stake in the present case. The riverfly, in its encounters with microplastics, fish, birds, algae, water, concerned citizens and wastewater works, becomes an "interscalar vehicle" for the analysis of the many scales in which ecological phenomena occur, from the scale of one larval case to the deep time reflections offered by fossil remains.

The riverfly itself becomes a sensor for the condition of the urban landscape. What this story brings to light is not only that flies are useful indicators for environmental assessment, but also that flies have been affected by the degradation of river habitats since the dawn of human civilization. Flies require their own kind of environmental justice.

The River Thames has been conditioned and remade in indelible ways, including from the large-scale dumping of wastewater. Assuming the vantage of the riverfly requires us to consider what a multispecies justice might look like - an environmental justice that does not foreground a human perspective, but rather imagines how humans might better cohabitate with other living beings.