Stream Bugs of Montgomery County
Montgomery County is home to hundreds of species of aquatic bugs (Benthic Macroinvertebrates). These aquatic bugs process nutrients and energy, powering the stream ecosystem! Because they are crucial to the stream, they are excellent indicators of stream health.
What is a Benthic Macroinvertebrate or Stream Bug?
Why Call them Benthic Macroinvertebrates?
Benthic = bottom dwelling
Macro = visible without a microscope
Invertebrates = lack a backbone
Why are Stream Bugs Important?
Stream bugs are an important member of aquatic communities. Many stream bugs eat aquatic plants, algae, and terrestrial plants that fall into the water. Those bugs form the base of the food chain and are called Shredders.
Stream bugs are great indicators of stream health, because they:
Stream Bug Groups
Montgomery County categorizes stream bugs into groups based on their ability to withstand pollution. Each genus has a unique tolerance value that helps DEP assess the health of our streams.
Common Stream Bug Groups (Orders)
Want to learn more about benthic macroinvertebrates? Check out the DNR Factsheet (PDF, 1.40MB)
Monitoring for Stream Bugs
DEP collects samples of benthic macroinvertebrates in order to gauge the health of the stream. Using their hands, stream rakes and other tools, DEP staff members shake loose the stream bugs from the rocks they cling to within the stream and catch them downstream in nets. The different stream bugs are then identified in the lab. For a full, detailed explanation of this process, watch the video below.
What Data Does DEP Collect?
DEP collects a sample of benthic macroinvertebrates from the stream and returns to the laboratory for further sub-sampling. Individuals from the sub-sample are identified (usually to the genus level) and enumerated. From these data, metrics are calculated, scored, and then summed to obtain a final Benthic IBI score.
There are a total of eight metrics comprising measures of biological structure and function; each metric is scored either as a one, three, or five. The highest possible final score is 40 (5 x 8). To determine the overall stream condition, benthic IBIs are averaged with fish IBIs.
* EPT = taxa that are either mayflies (Ephemoptera), stoneflies (Plecoptera), or caddisflies (Trichoptera); aquatic insects that spend all of their juvenile or larval life stages instream.
To determine a narrative based on a final metric score, the following breaks are used. These breaks are determined by plotting reference stream benthic conditions.
Available Benthic Data
Montgomery County has tabular raw benthic data and benthic narrative summaries from 1994-present for most monitoring sites. Also available are GIS coverages (or maps) showing benthic conditions. Maps can be made to order depending on the request.
Interested in other DEP monitoring data? Visit our Monitoring webpage for a list of the different monitoring data sets the County collects.