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Macroinvertebrates home

Streams project

 

Stone Bridge Brook (LCD_StnBrBrk_133)

These are the most common macroinvertebrates identified from samples from Stone Bridge Brook.

Click on images to zoom in. 

ORDER: Trichoptera
FAMILY: Philopotamidae

GENUS: Chimarra

Chimarra are distinguished from the other Philopotamidae by a prominent asymmetrical notch in the frontoclypeus as well as a prominent process on the femora which bears a single hair (seta). SMC


ORDER: Trichoptera
FAMILY: Hydropsychidae

This family of net-spinning caddisflies is very abundant at several sites.  They are important filtering collectors and are quite common at urban and agricultural sites where particles of organic material can be important food resources.  Genus-level identification is possible for mature specimens and we will include the genera we found at your site if possible. Commonly found genera include Cheumatopsyche, Ceratopsyche, and Hydropsyche. Less commonly, we have found Arctopsyche and Potamyia.

When using the key, some features that are challenging to see are the forked trochantin and the paired sclerites in the folds between segments.  Other, more easily seen key features include filamentous gills on the abdominal segments and the sclerotization of the dorsal surfaces of all three thoracic segments. Keep in mind that with smaller or more immature specimens, genus-level ID may not be possible.


ORDER: Ephemeroptera
FAMILY: Baetidae
 

This mayfly has either two or three cerci ("tails") and a unique head shape. Its gills are oval shaped and insert dorsally.

Commonly encountered genera include Acerpenna, Baetis, and Pseudocloeon.

ORDER: Diptera
FAMILY: Chironomidae

 Midge larvae tend to be the most common macroinvertebrate at our sites.  As with other Diptera, there are no true jointed legs.  Chironomidae do have a pair of prolegs at each end and preserved individuals tend to curl into a 'C'.  Identification past family requires slide-mounted heads.  We have seen philopotamid caddisflies misidentified with the chironomids and we suspect that that happens when samples are being sorted from trays.  Under a microscope, six prominent legs can be seen on members of the family Philopotamidae.

ORDER: Coleoptera
FAM
ILY: Psephenidae
GEN
US:
Psephenus

The true "water penny" is commonly found in the waters sampled. Psephenus has a rounded shape with relatively smooth edge. The false water penny, whose edges are serrated, has a more oval appearance. The gills on the ventral surface are found only in the true water pennies. SMC

Another genus encountered in this family is Ectopria.

 

ORDER: Ephemeroptera
FAM
ILY: Isonychiidae
GEN
US: Isonychia

This mayfly has unique long hairs on its forelegs as the main distinguishing characteristic (allowing anyone keying to move through quickly). Carefully observe the limbs because such hair can be matted down and therefore hidden in preserved wet specimens. The body of Isonychia is slim and "minnow-like" when observed dorsally. In specimens we collected, they were commonly brown and substantial in length and width as compared to the very common Baetidae. Some individuals are immature, but upon closer inspection one can see the setae on the forelegs.

ORDER: Ephemeroptera
FAMILY: Baetidae 
GENUS: Baetis 

This mayfly has three "tails" and a unique head shape. Its gills are oval shaped and insert dorsally. More mature nymphs have long, dark wing pads. SMC

ORDER: Coleoptera
FAMILY: Elmidae
GENUS: Stenelmis

The larvae of Stenelmis, as in Ordobrevia, have a sternum on the ventral side of the pronotum. The main difference between the two genera is in the antennae- the second segment is less than twice as long as the first in Stenelmis.

The adult Stenelmis has a clear separation between the thorax and abdomen as well as a more distinctly separate head as compared to other genera. SMC

ORDER: Ephemeroptera
FAMILY: Heptageniidae
Genus: Maccaffertium
 

This genus of Heptageniidae is distinguished by its gills on the seventh abdominal segment, which are reduced to slender filaments. Gills on segments 1-6 are truncated.

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ORDER: Trichoptera
FAMILY:
Hydropsychidae
GENUS: Ceratopsyche

Ceratopsyche has a forked foretrochantin. The foretrochantin is the projection at the uppermost portion of the foreleg. The leg may need to be pulled away from the body to expose this feature.

Ceratopsyche have a large pair of sclerites underneath the prosternum. Note: the large single sclerite is the prosternal plate. SMC

 

 

ORDER: Plecoptera
FAMILY: Perlidae
GENUS: Agnetina

The Agnetina has a rounded abdomen that appears to striped. The key defining characteristic is the three ocelli on the dorsum of the head (3 black dots at joint with the prosternum). Like other Plecoptera, it has 2 tails and 2 claws on its tarsi. SMC

This stonefly is characterized by the filamentous gills located in the "armpits". Another important feature is the paraglossae and glossae extending different lengths. The occiput has a transverse row of evenly spaced little hairs. Agnetina has another row of evenly spaced hairs on the posterior edge of abdominal segment 7.


 

ORDER: Trichoptera
FAMILY: Hydropsychidae
GENUS: Hydropsyche

Hydropsyche share most characteristics with Ceratopsyche, including the sclerites in the intersegmental folds. Hydropsyche are distinguished from Ceratopsyche by the presence of scale hairs and minute spines on the three most posterior abdominal segments. SMC

ORDER: Coleoptera 
FAMILY: Elmidae
GENUS:
Optioservus

The larvae of Optioservus have open coxae, as determined by the straight definition between segments on the ventral side of the pronotum.

The adult Optioservus have a compact appearance, especially the head and thorax. There are also dorsal ridges and a characteristic diamond-shaped scutellum observable in the dorsal view.
SMC

 


ORDER: Diptera
FAMILY: Ceratopogonidae

Members of this family look like very straight Chironomidae. They are very long and thin with a distinct head capsule and no prolegs.  Some in the lab call them 'bamboo sticks with eyes.' SMC

ORDER: Megaloptera
FAMILY: Corydalidae
GENUS: Nigronia

Members of the genus Nigronia share some superficial commonalities with Trichoptera, but on careful inspection one can see the two pairs of anal claws that help place it in the order Megaloptera.  The size of mature larvae is impressive; specimens from other genera exceed 8 cm in length.  The abdominal segments have ribbon-like gills on the lateral portions. The mouth has mandibles that are serrated and used for biting prey.  They can be confused with the more slender whirligig beetle larvae; whirligig larvae also have simpler jaws  SMC

The images are not a substitute for keying, but should serve as an aid in identifying common macroinvertebrates in samples.

Feedback - Partner schools: send us specimens not included above.  Taxonomists: click to email: Declan McCabe
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