Wednesday, October 18, 2017

A "Cheat Sheet" for the flatheaded mayflies (Heptageniidae)


While genus ID for most EPT taxa requires microscope work, there are a number of families where the genus can be nailed down by volunteers that monitor streams, certainly if they're using a loupe.  That is the case for the Heptageniidae -- flatheaded mayflies -- so I've worked up a cheat sheet for those who might want give this a try.  Just be advised, that this only applies to the flatheaded genera I've seen.  The two I've not yet encountered are Macdunnoa and Stenonema.  Both are type 1.

                                        Cheat sheet for flatheaded mayflies

 1.  with thin, single filament gills on segment 7

a. Maccaffertium (most are mottled with banded legs); gills truncate
b. Stenacron (uniform in color – gray/dark brown, though some have stripes on abdomen); gills pointed, abdomen long and thin
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2. with "fan-like" gills that overlap ("suction cup" gills)

a. 2 tailsEpeorus
b. 3 tails with fibrilliform on top of gills – Rhithrogena
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3.  gills stick out to the sides, don't overlap

a. fibrilliform present on all gills – Heptagenia
b. no fibrilliform on final gill, head very wide; small mayfly: Leucrocuta (common)
c. no fibrilliform on final gill, intersegmental setae present on cerci (probably need microscope): Nixe (uncommon)
d. maxillary palps visible on sides of head -- Cinygmula

Let's give it a try.

1. with thin, single filament gills on segment 7

a. Maccaffertium


b. Stenacron




One caveat: there is one Maccaffertium species -- modestum -- that does not fit into the "mottled" mold and could be confused with Stenacron (I've made the mistake).  But, the color differs markedly  from the Stenacron nymphs that we see.

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2. with "fan-like" gills that overlap ("suction cup" gills)

a. Epeorus.  If there are only two tails this call's a slam dunk.


b. Rhithrogena


The "fan" of the gills is not so prominent on these nymphs, but the "fibrilliform" (frilly filaments) on the tops of the gills is easy to see.  Both Epeorus and Rhithrogena have "suction cup" gills.  You can see this with a loupe (though this is a microscope view.)


Epeorus and Rhithrogena are "clingers" that use those gills to hold on to the rocks in fast water.
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3.  gills stick out to the sides, don't overlap

a. Heptagenia.  You can see those "frilly filaments" behind each of the gills.


b. Leucrocuta.  There are strands of filaments (nothing like the fibrilliform on the Heptagenia nymphs) behind the gills on segments 1-6.  They're absent on 7.


Leucrocuta nymphs are pretty darn small, and as you can see they have very wide heads.  (That's also Leucrocuta at the top of the page.)

c. Nixe.  This genus is uncommon.   I've only seen it in the Pacific Northwest, but according to Beaty they are found here on occasion.


Nixe cannot be distinguished from Leucrocuta out in the field.  It takes a microscope to see the "intercalary setae" on the cerci (tails), present on Nixe, absent on Leucrocuta


 Still, it's a safe bet that the "fatheaded" flatheads you find are genus Leucrocuta.

d. Cinygmula.  


I can tell this one at sight -- others might need a loupe.  Look for two bumps on the sides of the head, the maxillary palps.

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Not so tough after all, right?  And it might add to your enjoyment of picking bugs off the net!   Which genus are you most likely to see?  Maccaffertium, no doubt about it.  These nymphs are in our streams year round, the other genera are seasonal, generally speaking in spring and summer. 

Sunday, October 15, 2017

The "ventral apotome" and genus ID of caddisfly larvae


I've been working with a friend who wants to learn EPT genus level ID, and I've been struck by the number of cases in which the "ventral apotome" -- also known as the "gular sclerite" -- is one of the keys to the genus.  The ventral apotome is a sclerite on the venter of the head, as you can see in this illustration.


(The "gula" on the larva is "the ventral region between the base of the beak and the collar." [Merritt, Cummins, and Berg, ed., An Introduction to the Aquatic Insects of North America, 4th edition, p. 996.])

While I can't be sure that I have any readers who find this of interest, for those who might, here's how this is used when we identify a caddisfly larva to the level of genus.
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1. Hydropsychidae, genus Arctopsyche (the larva in the photo at the top of the page.)  This is a common netspinner that I find in Montana, but it does occur in our region even though I've not come across it so far.


In this case, the sclerite runs the length of the gula, but the critical factor is that it narrows from top to bottom.
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2. Hydropsychidae, genus Parapsyche.  Another netspinner that apparently occurs in our region, but again one that so far I've not seen.  This larva is one that I found in Oregon.  (Unfortunately, for this one I don't have a live photo.)


The ventral apotome again runs the length of the gula, but it narrows only slightly from top to bottom, more rectangular in shape.


With Arctopsyche and Parapsyche, the ventral apotome is the only thing you need to see to determine the genus ID.
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3.  Hydropsychidae, genus Cheumatopsyche.  This is a netspinner we see a lot in our streams: our stream monitors will recognize this one for sure.


While the ventral apotome is not the only thing we need for our genus ID, it's where we begin.


The ventral apotome can consist of an anterior sclerite and a posterior sclerite or simply one or the other.  Here it is the anterior sclerite on which we must focus.  No tubercle -- a bump on the middle of the top of the sclerite.
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4. One more netspinner -- Hydropsychidae, genus Hydropsyche -- the most common, common netspinner that we see in our streams. 


To be fair, it's not the ventral apotome that's important on this one.  Rather, we look for a pair of sclerites below the "prosternal plate," kind of the "neck" instead of the gula.


And that's all you need to see.
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5. Lepidostomatidae, genus Lepidostoma and genus Theliopsyche. 



Lepidostoma is very common in forested streams -- cold water streams in the mountains -- throughout the winter and into the spring.  (We're not sure that those that we see in late spring/early summer are the same species that we see in the winter: probably not.)  Theliopsyche, however, is not at all common: I've only seen one (possibly two).



The two differ, as you can see, by the size of the ventral apotome, and the length of the median ecdysial line. 
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6. Uenoidae, genus Neophylax


This is another taxon that we see a lot in the winter in the very same streams we find Lepidostomatidae.  It prefers those cold mountain streams, though some are found in streams that are not at the very top tier (e.g. Doyles River and Buck Mt. Creek).  Neophylax used to be a Limnephilidae genus; but now it's a family -- Uenoidae -- all on its own.   The ventral apotome is one of two things we use to establishing genus (Neophylax) ID.


The gular sclerite is unique being shaped like a "T".
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7. One more, the "humpless" casemaker (Brachycentridae), genus Micrasema.


One of the keys to genus ID -- the ventral apotome is wider than it is long.

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So there you have it.  I hope some of you find this instructive.  When you pick up a caddisfly larva -- one of the above anyway -- take a peek under the head.  Useful information down there.

Sunday, October 8, 2017

And already a new one to add: Long-horned casemaker, Oecetis avara


While going through some vials I had tucked away in my lab, I just found this little larva (5mm).  I knew right away that it was a long-horned caddisfly -- the length of the hind legs tells us that much -- but the case is one that I don't remember seeing before.


Hmm... time to look at our key.  (p. 356)

141 Maxillary palpi extending far beyond labrum; mandibles long and blade-like with sharp apical tooth separated from remainder of teeth; cases of various types and materials....Oecetis

Oecetis for sure.


On to the species. (p. 370)

171  Dorsal hump of abdominal segment 1 with 4-6 rows of micro-hooks on each side....Oecetis (Pseudosetodes) avara

171' Dorsal hump of abdominal segment 1 without micro-hooks..... 172

Have a look.


If only every ID were so easy!  Oecetis avara.  Just for fun, I thought I'd look at Steve Beaty's description as well.  ("The Trichoptera of North Carolina," p. 92)

O. avara -- larvae 6.5-9 mm; dorsal hump with 4-6 rows of conspicuous micro-hooks on each side.  Case of sand, tapered, an curved in early instars.  Lotic.  Uncommon in the Mountains and Sandhills.

Well, the key feature -- the rows of micro-hooks -- is exactly the same, but our larva is quite a bit smaller, and our case is clearly not made of sand.  The size can be explained -- our larva is possibly immature.  As for the case...hmm... could it be that even though our larva is still pretty small, it no longer lives in the type of case used by "early instars"?  That's the only way that I can explain it.

I'm disappointed that I don't seem to have a live photo of this larva.  There are two possibilities for why that is so.  1) I had put this case into a vial before I saw what it was (trust me, I've done it!), and 2) it's a larva that's been in my possession from the time that I still worked with StreamWatch 7 long years ago.  In any event, the ID is certain, and it's certain that it was found in some local stream.  I've added it to our list of EPT species.
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Additional notes:
Since writing this entry this morning, I've done some additional work, looking at Roger Rohrbeck's website, Pacific Northwest Caddisflies (http://www.flyfishingentomology.com/PNW%20Caddisflies.htm).  Two things.  1) On the case he comments: "case curved cones made of rock fragments and sand, or pieces of plant or twigs. (emphasis added by me.)  And at another location (http://www.flyfishingentomology.com/WACaddisflyDescription.php?Fa=Leptoceridae&Ge=Oecetis),  he shows a case for Oecetis that is exactly like the one that I found in my vial.
Also,  let me quote from Wiggins (Larvae of the North American Caddisfly Genera, 1st edition (1977), p. 172): "Larval cases of Oecetis species are varied in both form and materials: small fragments of rock often combined with bark or leaves; and short lengths of stems and twigs placed transversely."  No longer see our case as a problem.

EPT List for Central Virginia, 2017


Not yet -- but pretty soon we'll see those beautiful colors of autumn.

Since readers on occasion look at the EPT list that I posted in 2012, I thought I should probably update that list in this entry.    Included are additions and corrections, and in some cases taxa names have been changed by entomologists.  Also included are taxa I've seen but others have found all duly noted.  As I did for awhile with the entry of 2012, I will try to go back to this list and make changes as they occur: I'll note such changes in future postings.  Please be clear that this is not an "official" list of EPT taxa that are here; it's a list of the taxa that I've found, including some things that have been found by my friends.

                   EPT Species List for Central Virginia
                   (Albemarle, Greene, Madison, Fluvanna)
                 
I. Ephemeroptera (Mayflies)

1. Ameletidae

1. Ameletus lineatus

2. Baetidae (Small minnow mayflies)

1. Acentrella nadineae
2. Acentrella turbida
3. Baetis flavistriga
4. Baetis intercalaris
5. Baetis pluto
6. Baetis tricaudatus
7. Heterocloeon curiosum
8. Heterocloeon amplum
9. Heterocloeon petersi
10. Iswaeon anoka
11. Labiobaetis propinquus
12. Plauditus dubius

3. Isonychiidae (Brushlegged mayflies)

1. Isonychia sp. (bicolor? probably more than one species)

4. Heptageniidae (Flatheaded mayflies)

1. Cinygmula subaequalis
2. Epeorus pleuralis
3. Epeorus vitreus
4. Epeorus fragilis
5. Heptagenia marginalis
6. Leucrocuta hebe
7. Leucrocuta sp.
8. Leucrocuta aphrodite
9. Leucrocuta thetis
10. Maccaffertium ithaca
11. Maccaffertium merririvulanum
12. Maccaffertium pudicum
13. Maccaffertium vicarium
14. Maccaffertium modestum
15. Rhithrogena sp. (at least two species have been found; one appears to be exilis)
16. Stenacron carolina
17. Stenacron interpunctatum

5.  Ephemerellidae (Spiny crawler mayflies)

1. Drunella cornutella
2. Drunella tubercula
3. Drunella walkeri
4. Ephemerella dorothea
5. Ephemerella invaria
6. Ephemerella subvaria
7. Eurylophella verisimilis
8. Eurylophella funeralis (found by DB)
9. Eurylophella sp. (minimella?) (found by DB)
10. Serratella serratoides
11. Serratella serrata
12. Teloganopsis deficiens

6. Baetiscidae (Armored mayflies)

1. Baetisca berneri

7. Caenidae

(I saw a lot of Caenidae when I was with StreamWatch: not a one since then.  I hope to correct this so I can determine genus and species.)

8. Leptohyphidae (Little stout crawler mayflies)

1. Tricorythodes

9. Leptophlebiidae (Pronggilled mayflies)

1. Neoleptophlebia assimilis
2. Paraleptophlebia guttata
3. Paraleptophlebia sp.  (jeanae?)
4. Paraleptophlebia strigula
5. Habrophlebia vibrans
6. Leptophlebia sp.

10. Ephemeridae (Common burrower mayflies)

1. Ephemera guttalata


II. Plecoptera (Stoneflies)

1. Capniidae (Small winter stoneflies)

1. Allocapnia sp. (pygmaea?)
2. Paracapnia angulata

2. Leuctridae (Needleflies)

1. Leuctra sp.

3. Nemouridae (Forestflies)

1. Amphinemura delosa
2. Prostoia completa
3. Soyedina sp.(carolinensis?)

4. Taeniopterygidae (Large winter stoneflies)

1. Strophopteryx fasciata
2. Taenionema atlanticum
3. Taeniopteryx burksi/maura

5.  Chloroperlidae (Green stoneflies)

1. Alloperla sp.
2. Haploperla brevis
3. Sweltsa sp.

6. Peltoperlidae (Roach-like stoneflies)

1. Peltoperla sp.
2. Tallaperla sp.
3. Viehoperla sp. (found by DB)

7. Perlidae (Common stoneflies)

1. Acroneuria abnormis (brown)
2. Acroneuria abnormis (patterned)
3. Acroneuria carolinensis
4. Acroneuria sp. (possibly internata, possibly a variety of abnormis)
5. Acroneuria arenosa
6. Acroneuria lycorias
7. Agnetina annulipes
8. Agnetina capitata
9. Agnetina flavescens
10. Eccoptura xanthenses
11. Neoperla sp. (clymene?)
12. Paragnetina immarginata
13. Paragnetina fumosa
14. Perlesta sp. (various species)

8. Perlodidae (Springflies and Stripetails)

1. Clioperla clio
2. Diploperla duplicata
3. Helopicus subvarians
4. Isogenoides hansoni
5. Isoperla dicala
6. Isoperla holochlora (light form)
7. Isoperla holochlora (dark form)
8. Isoperla latta/pseudolatta
9. Isoperla kirchneri group
   (probably both I. kirchneri and I. montana)
10. Isoperla similis/prosimilis group
11. Isoperla davisi
12. Isoperla orata
13. Isoperla orata (variant form)
14. Isoperla sp.VA
15. Malirekus hastatus
16. Rememus bilobatus

9. Pteronarcys (Giant stoneflies)

1. Pteronarcys biloba
2. Pteronarcys dorsata
3. Pteronarcys proteus


III. Trichoptera (Caddisflies)

1. Rhyacophilidae (Free-living caddisflies)

1. Rhyacophila carolina
2. Rhyacophlia fuscula
3. Rhyacophila nigrita
4. Rhyacophila glaberrima
5. Rhyacophila fenestra
6. Rhyacophila sp. (banksi?)

2. Glossosomatidae (Saddle-case makers)

1. Glossosoma nigrior

3. Philopotamidae (Fingernet caddisflies)

1. Chimarra sp.
2. Dolophilodes distincta
3. Wormaldia sp.

4. Polycentropodidae

1. Polycentropus sp.

5. Hydropsychidae (Common Netspinners)

1. Ceratopsyche alhedra
2. Ceratopsyche bronta
3. Ceratopsyche morosa
4. Ceratopsyche slossonae
5. Ceratopsyche sparna
6. Cheumatopsyche sp.
7. Diplectrona modesta
8. Diplectrona metaqui (found by DB)
9. Hydropsyche betteni
10. Hydropsyche rossi
11. Hydropsyche venularis
12. Macrostemum carolina

6. Brachycentridae (Humpless case-makers)

1. Adicrophleps hitchcocki
2. Brachycentrus appalachia
3. Micrasema wataga
4. Micrasema charonis
5. Micrasema bennetti

9. Lepidostomatidae

1. Lepidostoma sp. (at least 2 species, possibly more)
2. Theliopsyche sp.

10. Limnephilidae (Northern case-makers)

1. Pycnopsyche gentilis
2. Pycnopsyche scabripennis
3. Pycnopsyche luculenta
4. Pseudostenophalyx sparsus

11. Apataniidae

1. Apatania incerta

12. Goeridae

1. Goera calcarata
2. Goera fuscula

 13. Uenoidae

1. Neophylax oligius
2. Neophylax consimillis
3. Neophylax aniqua
4. Neophylax mitchelli
5. Neophylax fuscus
6. Neophylax concinnus

14. Leptoceridae (Long-horned case-makers)

1. Nectopsyche equisita
2. Ceraclea maculata
3. Oecetis avara

15. Odontoceridae (Strong case-makers)

1. Psilotreta labida
2. Psilotreta frontalis
3. Psilotreta rufa (found by DB)

16. Molannidae (Hooded-case maker)

1. Molanna blenda (found by DB)

17. Calamoceratidae (found by StreamWatch monitors)


1. Anisocentropus pyraloides