This document provides identification keys for selecting and identifying common aquatic insect larvae and nymphs found in streams and rivers. It includes keys for mayfly, dragonfly, damselfly, stonefly, caddisfly, beetle, crane fly larvae, and true fly pupae. Each key walks through a series of dichotomous choices based on morphological characteristics to determine the insect's family. Accompanying each choice are short descriptions and photos to illustrate the distinguishing features.
6. 1B. Head not flattened, eyes and antennae lateral … 2
1C. Unclear if head is flattened … preserve
http://www.troutnut.com/specimen/694
7. 2A. Prothoracic legs (first set of legs) with a dense row of setae
(hair) along inner surface … Brushlegged (Isonychiidae)
http://www.entomology.umn.edu/midge/VSMIVP%20K
ey/English/Isonychiidae.htm
http://www.pbase.com/tmurray74/image/114911606
9. 2B. Prothoracic legs without setae … 3
2C. Unclear if prothoracic legs have setae … preserve
http://bugguide.net/node/view/49022/bgimage
10. 3A. Median caudal filament (Middle tail) reduced or lacking
…Small Minnow (Baetidae)
http://www.pbase.com/tmurray74/image/110648170
http://www.pbase.com/tmurray74/image/114367511
11. 3B. Median caudal filament well developed … 4
3C. Unclear if median caudal filament is present, possibility of
broken tail … preserve
http://www.troutnut.com/specimen/443
12. 4A. Gills pronged, forked, or consisting of a slender filament …
Prong-gilled (Leptophlebiidae)
http://www.entomology.umn.edu/mi
dge/VSMIVP%20Key/English/Lepto
phlebiidae.htm
http://www.pbase.com/tmurray74/image/1 http://www.pbase.com/tmurray74/i
10909718 mage/59402763
13. 4B. Gills round, oval or heart-shaped – not forked … 5
4C. Gill shape is unclear … preserve
http://bugguide.net/node/view/266381/bgimage
http://www.troutnut.com/specimen/718
15. 5B. Gills absent from abdominal segment 2, rudimentary or
absent from segment 1 and sometimes absent from segment 3 …
Spiny Crawler (Ephemerellidae)
3
4
5
6
http://bugguide.net/node/view/259874
17. 5C. Gills are operculate, or unclear if gills are present on
segments 1-3 … preserve
http://www.entomology.umn.edu/midge/VSMIVP%2 http://www.dfg.ca.gov/abl/images2/Tri
0Key/English/Caenidae.htm corythodes_gills2.png
http://www.troutnut.com/specimen/568 http://www.dfg.ca.gov/abl/images2/Tricorythodes_newhabitus2.png
18. Key to select dragonfly larvae
http://www.pbase.com/tmurray74/image/111213357
20. 1A. Third segment of antenna is much larger and possibly a
different shape than the other sements (4th segment is small and
barely visible) … Clubtail (Gomphidae)
http://www.entomology.umn.edu/midge/VSMIVP%20Key
/English/Gomphidae.htm
http://bugguide.net/node/view/263809/bgimage
22. 1B. Third segment of antenna not larger than other segments … 2
1C. Unclear if 3rd segment is larger … preserve
http://bugguide.net/node/view/255141/bgimage
23. 2A. Prementum (lower lip) flat when viewed from the side. When
viewed ventrally, prementum is widest in distal half but not
parallel sided … Darner (Aeshnidae)
http://www.entomology.umn.edu/midge/VSMIVP% http://www.pbase.com/tmurray74/image/109642026
20Key/English/Aeshnidae.htm
25. 2B. Prementum spoon/scoop shaped when viewed from the side
… preserve
2C. Unclear if prementum is flat or spoon shaped … preserve
http://www.entomology.umn.edu/midge/VSMIVP%20Key/English/Cordulegastridae.htm
26. Key to select damselfly larvae
http://bugguide.net/node/view/260089/bgimage
28. 1A. First segment of antenna is as long as, or longer than,
remaining segments combined … Broadwinged (Calopterygidae)
http://www.entomology.umn.ed
u/midge/VSMIVP%20Key/Engli
sh/Calopterygidae.htm
Rose Brown photo: Rivanna at Milton
29. 1B. First segment of antenna is shorter than others combined … 2
1C. Unclear if first segments of antennae are long … preserve
http://www.dfg.ca.gov/abl/images2/archilestes_head.png
30. 2A. Basal half of prementum greatly narrowed and elongate …
Spreadwinged (Lestidae)
http://www.entomology.umn.edu/m
idge/VSMIVP%20Key/English/Lesti
dae.htm
http://www.pbase.com/tmurray74/image/95281414
31. 2B. Basal half of prementum not greatly narrowed …
Narrowwinged(Coenagrionidae)
2C. Unclear if prementum is narrowed … preserve
http://www.entomology.umn.edu/mi
dge/VSMIVP%20Key/English/Coen
agrionidae.htm
http://bugguide.net/node/view/255064/bgimage
32. Key to select stonefly larvae
http://www.troutnut.com/specimen/487
34. 1A. Filamentous or Telescoping gills present on sides of thorax
and/or ventral thorax … 2
http://www.entomology.umn.edu/midge/VSMIVP
%20Key/English/Perlidae.htm
http://www.entomology.umn.edu/midge/VSMIVP%20
http://www.troutnut.com/specimen/350 Key/English/Pteronarcyidae.htm
35. 1B. Filamentous gills present only on ventral cervix (neck) …
Nemourid (Nemouridae)
1C. Unclear if gills are present … preserve
www.aquatax.ca/plecoptera/Nemouri
daeGills.jpg
http://www.pbase.com/tmurray74/image/110935526
36. 2A. Conspicuous filamentous gills present on sides of thorax
and/or ventral thorax … 3
http://www.entomology.umn.edu/midge/VSMIVP%
20Key/English/Perlidae.htm
http://www.entomology.umn.edu/midge/VSMIVP%20Key/E
nglish/Pteronarcyidae.htm
37. 2B. One telescoping gill present at base of each leg … Large
Winter(Taeniopterygidae)
2C. Unclear if gills are present … preserve
http://www.troutnut.com/specimen/350 http://www.troutnut.com/specimen/350
38. 3A. Filamentous gills present on ventral abdominal segments 1
and 2 … Giant (Pteronarcyidae)
http://www.troutnut.com/specimen/334
http://www.troutnut.com/specimen/334
39. 3B. Filamentous gills absent from abdomen … Common
(Perlidae)
http://www.troutnut.com/specimen/767 http://www.troutnut.com/specimen/767
40. 3C. Unclear if gills are present on ventral thorax and/or abdomen
… preserve
http://www.troutnut.com/specimen/488
41. Key to select caddisfly larvae
http://www.pbase.com/tmurray74/image/95399019
43. 1A. Caddisfly in a case … 2
http://www.pbase.com/tmurray74/image/110473352
Rose Brown photo
44. 1B. Caddisfly not in a case … 3
http://www.troutnut.com/specimen/720
45. 2A. Case is a dome of small rock particles that completely covers larva in dorsal
(top) view. On the ventral (under) side, there is a strap of smaller rock particles.
The larva hangs over the strap, with head and thorax on one side and the end of
the abdomen on the other side (both ends of larva are visible) … Saddle Case Maker
(Glossosomatidae)
http://www.dfg.ca.gov/ABL/images2/anagapetus_case.png
http://www.dfg.ca.gov/abl/images2/gloscas1.png
46. 2B. Case is very small, composed of fine sand or silt. Case is constructed with
two similar halves and compressed from side to side, resembling a purse …
Micro Caddisfly (Hydroptilidae)
http://watermonitoring.uwex.edu/images/level1/
wav/ecology/Hydroptilidae.jpg
http://www.dfg.ca.gov/abl/images2/hydroptila_habitus_
withcase.png
47. 2C. Case is unlike above, or difficult to see … preserve
http://www.pbase.com/tmurray74/image/111399160
http://www.pbase.com/tmurray74/image/109997968
48. 3A. Larva is bright yellow-orange. The tops of the second and third thoracic
segments are soft and fleshy, without hardened plates … Fingernet
(Philopotamidae)
http://www.pbase.com/tmurray74/image/111032573
49. 3B. Larva is bright green and has long abdomen with deep constrictions
at each segment (best seen in top view). The tops of the second and
third thoracic segments are soft and fleshy, without hardened plates.
No filamentous gills on abdomen … Freeliving (Rhyacophilidae)
http://www.pbase.com/tmurray74/image/110921297
50. 3C. Larva is not bright yellow-orange or green, or color and
shape are unclear … preserve
http://www.pbase.com/tmurray74/image/110921300
http://www.pbase.com/tmurray74/image/109167612
51. Key to select beetles
http://www.dfg.ca.gov/abl/images2/ptilodactylidae_adult_habitus.png
54. 1B. Larval beetle … 3
1C. Unclear if beetle is adult or larval … preserve
http://www.pbase.com/tmurray74/image/114344092
55. 2A. Beetle has slender and long antennae, which are longer than
head … Riffle (Elmidae)
http://www.pbase.com/tmurray74/image/114324576
56. 2B. Beetle has short, thick antennae which are sometimes not
visible … Long Toed (Dryopid)
http://bugguide.net/node/view/171214
57. 2C. Antennae are unclear, possibility of broken antennae …
preserve
http://www.dfg.ca.gov/abl/images2/helichus_adult_dors http://www.pbase.com/tmurray74/image/114807295
al.png
58. 3A. Larval body is elongate, cylindrical and sclerotized
(hardened). Abdominal segment 9 with a tuft of filamentous gills
and a hard, moveable ventral operculum … Riffle (Elmidae)
http://www.dfg.ca.gov/abl/images2/zaitzevia_habitus.png
http://www.dfg.ca.gov/abl/images2/microcylloepus_operc
ulum.png
59. 3B. Larval body is elongate, cylindrical and sclerotized.
Abdominal segment 9 with a tuft of filamentous gills, and no
ventral operculum … (Ptilodactylidae)
http://www.dfg.ca.gov/abl/images2/ptilodactylidae_larva_habit
us2.png
http://www.dfg.ca.gov/abl/images2/ptilodactyl
idae_larva_gills.png
60. 3C. Larva is not like above … preserve
http://www.pbase.com/tmurray74/image/111183241
61. Crane Fly larva and True Fly pupae
http://ecology.hku.hk/jupas/Hexatoma%20sp.jpg