Sunday, October 12, 2014

The seasons of the caddisfly case-makers

As you know, at the moment I'm seeing a lot of case-makers: humpless case-makers (Brachycentrids), strong-case makers (Odontocerids), and weighted-case makers (Goerids).  Case-makers show up in our streams in fairly predictable ways: I know when -- at what time of year -- I will see what.  True, there are some exceptions, notably the humpless case-maker Brachycentrus appalachia and the saddle-case-makers, Glossossoma nigrior.  My photo archives reveal that I can run into these larvae at just about any month the year.  Still, this is the pattern I most commonly see.

I. Winter (into Spring)

1. Uenoidae (little northern case-makers): species found so far -- Neophylax aniqua, N. concinnus, N. consimilis, N. mitchelli (in photo at top of the page), and N. oligius.  I have found them from late November right into April; they're most prolific from December through March. Cases made out of sand grains and pebbles, with 3-4 larger pebbles on each of the sides.

N. consimilis

N. aniqua

N. oligius

2.  Apataniidae (little mountain case-makers): species -- Apatania incerta.   Cases are made of mineral particles.  They are often cornucopia shaped with a "hood" over the top of the larva.  To date, I have found them only in December and January.

3. Glossossomatidae (saddle-case maker): species found so far -- Glossossoma nigrior.  The case is "dome" shaped, made of pebbles; it resembles the shell of a turtle.  When you turn the case over you can see the larva lying under a "strap" or "saddle."  I see a lot of these in the winter -- December through March.  But, I also see them throughout the summer -- May through September.  The summer cases seem to be smaller than those that I see in the winter (= two generations?).

dorsal view

ventral view

4. Lepidostomatidae (common name, Lepidostomatid).  Species -- undetermined.  The case can be made out of sand grains (early instars), a mix of sand grains and neatly cut sections of leaves (transitional), or the common 4-sided case made of square pieces of leaves (mature larva).  I see them most often in small mountain streams from late November through May.  However, I've found some as late as June in remote mountain streams, and they also inhabit the Rivanna in the summer.

from the Rivanna in summer (probably a different species)

5. Limnephilidae (northern case-maker): species -- Pycnopsyche gentilis.  This caddis larva often makes a 3-sided case out of sections of leaves/bark.  But the case can be part leaves and part stones, or -- especially in the late spring -- a case that's completely made out of pebbles.  They're in our streams from January through May.   The cases are fairly large.

II. Spring (into Summer)

1. Limnephilidae (northern case-makers): species  -- Pycnopsyche scabripennis.  These larvae make fairly large cases using sticks and pieces of wood.  I have found them from April through August.  Cases really vary in appearance and composition.

(Petri dish is 3 1/2" in diameter.)

2. Limnephilidae (northern case-maker): species --  Pseudostenophylax sparsus.  This one was found by my friend in Sugar Hollow in a spring seep right by her home.  It's rare.  The case is made of sand and pebbles.  She found it in March, so it's borderline Winter/Spring.   I've found some in late May as well.

3. Brachycentridae (humpless case-makers).  Species found so far: Brachycentrus appalachia, Micrasema charonis, and Micrasema wataga.   B. appalachia makes a 4-sided "chimney-shaped" case out of ribbons of vegetation.  The Micrasema cases are round and tapered, composed of vegetation and moss.   B. appalachia will be discussed with the Fall case-makers.  I have only found one Micrasema charonis, and that was in April.  My friend in Sugar Hollow found M. wataga larvae in June.

M. charonis

M. wataga (photo provided)


III. Summer (into Fall)

1. Just a reminder -- I do find humpless case-makers (B. appalachia) throughout the summer, also saddle-case makers (small cases), and -- in the Rivanna -- Lepidostomatids.

2. Leptoceridae (long-horned case-makers): species found so far -- Nectopsyche exquisita and Ceraclea maculata.  N. exquisita is fairly common in the Rivanna with a case made of sand with plant stems attached.  I have found N. exquisita from July into October.  I have only seen C. maculata once, and that was in May.  (Guess I should put C. maculata into the Spring.)

N. exquisita

C. maculata


IV. Fall (into winter)

1. Brachycentridae (humpless case-maker): species -- Brachycentrus appalachia.  While I have found these cases just about every month of the year, they are common on the rocks at this time of year, with the larvae being mature (they hatch in the spring).   The cases I see in the summer are small. The case is attached to a rock with the opening facing upstream since the larvae lacks "humps" with which it could generate water flow.

and next to Apatania incerta

2. Brachycentridae (humpless case-maker): species -- Adicrophleps hitchcocki.  This was found by my friend in a very small, first-order stream, buried in moss.  It is rare and regarded as threatened in the state of Virginia.  The case resembles that of B. appalachia, with strands of moss attached.  She found this one in November.  (She took the photo.)

3. Odontoceridae (strong-case maker): species found so far -- Psilotreta labida and Psilotreta frontalis (and possibly P. rufa).   Cases are made out of pebbles that are tightly glued together, often tapered and curved.  I've seen them as early as July, but they're most common from September into November.  Their cases are easy to see since they lie on tops rocks.  Psilotreta frontalis is a species I've only seen once: end of October.

P. labida

P. frontalis

4. Goeridae (weighted case-maker): species -- Goera fuscula and Goera calcarata.  Fairly large cases -- larger than those of Uenoids -- that are made out of pebbles, with 2-4 large pebbles on each of the sides.  I've found them from August through November

G. calcarata (2-stone case)

G. fuscula (in a 4-stone case)


That's the case-maker cycle that I normally see -- at least in the stream work that I've done so far.  But if you monitor streams you want to be careful.    Things can show up "out of season," and you might find cases in the substrate long before they show up where I'm normally looking.   That being said, I've never seen a Uenoid in summer!

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