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Macroinvertebrates home

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Fall Brook (FMR_FallBrk_323)

These are the most common macroinvertebrates identified from samples from Fall Brook.

Click on images to zoom in. 

ORDER: Plecoptera
FAMILY: Leuctridae
GENUS: Leuctra

This family of stonefly is fairly slender by stonefly standards.  The divergent wing pads are a helpful characteristic. Leuctridae  are similar in overall shape to the Capniidae; however, Leuctridae often do not have pleural folds. If they are present, they only extend from abdominal segments 1-7.  Leuctra  are recognized by abdominal terga with posterior fringes of short hairs and last few segments with longer hairs. NABS

ORDER: Trichoptera
FAMILY: Rhyacophilidae
GENUS: Rhyacophila

In our lab, Rhyacophila is known as the "Michelin Man" due to its large banded body. It has a very obviously checker-patterned head. It also has a terrifying anal claw which has large accessory hooks. SMC

ORDER: Trichoptera
FAmily: Philopotamidae
Genus: Wormaldia
 

The distinguishing feature of members of this genus is an evenly convex frontoclypeus, as opposed to the deep notch in Chimarra or the wavy margin of the Dolophilodes.

ORDER: Diptera
FAMILY: Simuliidae

Simuliidae appear  rather like bowling pins with heads.  We have not identified them past family at this point, but it is in the long-term plan.

PHYLUM: Annelida
CLASS: Oligochaeta

Aquatic earthworms lack legs and are characterized by having 20 or more segments. Unlike leeches, they lack a suction disk.

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


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: 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.


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ORDER: Plecoptera
FAMILY: Pteronarcyidae
GENUS: Pteronarcys
 

Pteronarcyidae have branching gills from the bases of their legs as does Perlidae. What distinguishes Pteronarcyidae from Perlidae is the presence of gills on the first two abdominal segments. There are only two genera in this family, but the other, Pteronarcella, is only found in the west/southwest.

ORDER: Plecoptera
FAMILY: Perlidae
GENUS: Acroneuria

Acroneuria have postocular fringe consisting of many close-set thick spinules. They have three ocelli, and there is a yellow m-shaped mark in front of the middle ocellus. The bases of their cerci have thick, silky setae.

ORDER: Coleoptera
FAMILY:
Elmidae

We have found adult and larval riffle beetles. The adults are clearly beetles, but the larvae can be confused with other orders. The forward pointing tooth on the front end of the larvae as described in the key can be a challenge to see, particularly in small individuals.

Larvae are characterized by having a single tarsal claw at the end of their legs, which have 4 segments. Adults, on the other hand, have two tarsal claws at the end of each leg.

Commonly encountered genera include Dubiraphia, Macronychus, Optioservus, Phanocerus, Promoresia, and Stenelmis.

ORDER: Plecoptera
FAMILY: Leuctridae
GENUS: Megaleuctra

This family of stonefly is fairly slender by stonefly standards.  The divergent wing pads are a helpful characteristic. Leuctridae  are similar in overall shape to the Capniidae; however, Leuctridae often do not have pleural folds. If they are present, they only extend from abdominal segments 1-7. Compared to other Leuctridae, Megaleuctra is robust; its body is less than 8x its width. Its abdomen has many short setae. NABS

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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