Corresponding author: Boonsatien Boonsoong (
Academic editor: E. Dominguez
Nine genera and twenty-two species of heptageniid mayflies from Thailand are defined in this present work as well as one suggested further subgenus,
Heptageniid mayflies are one of the most abundant and common components of benthic communities in Thai running waters. The larvae inhabit slow to fast flowing streams where they occur on the surface of rocks, logs, vegetation, and leaves. Many heptageniid species have been used as indicators of anthropogenic disturbance because they are relatively intolerant of pollution change and as sensitive indicators of organic pollution (
In the following key and text, abbreviations are as follows: alt (altitude), asl (above sea level), μS/cm (microsiemens per centimeter), comb. (combination), M (male imago), F (female imago), mount. (mountainous), Ms (male subimago), Fs (female subimago), NP (National Park), orig. (original), sec. (second), WS (Wildlife Sanctuary).
1 | Median caudal filament absent ( |
|
– | Median caudal filament present | 8 |
2 | Lamellae of gills 2-7 with anal ribs arched ( |
subgenus |
− | Lamellae of gills 2-7 without anal ribs arched | 3 |
3 | Lamellae of gills 1 greatly extended beneath the abdomen ( |
subgenus |
– | Lamellae of gills 1 somewhat extended beneath the abdomen ( |
subgenus |
4 | Abdominal terga 2–9 each with long, acute median spine on posterior margin ( |
|
– | Abdominal terga 2–9 each without acute median spine on posterior margin ( |
|
5 | Abdominal terga with paired long acute submedian spines | |
– | Abdominal terga without paired acute submedian spines; foretibiae relatively long; median dark brown on the abdominal terga | |
6 | Pair of submedian spines on terga 2-9 relatively long ( |
|
– | Pair of submedian spines on terga 2-9 relatively short | 7 |
7 | Paired tubercles on terga rounded, blunt bristles densely rowed | |
− | Paired tubercles on terga more rounded, pointed bristles ( |
|
8 | Gill-pairs 1 meet or overlap ventrally to form a friction disc ( |
|
– | Gill-pairs 1 not meeting ventrally and not forming a ventral friction disc | 9 |
9 | Lamellae of gills 1 minute, lamellae of gills 2-7 long, narrow and sharply pointed ( |
|
– | Lamellae of gills 1 similar in shape and size to other gills; gill lamellae usually not as above; ventral surface of maxillae with scattered setae ( |
10 |
10 | Abdominal terga with median dorsal ridge ( |
|
– | Abdominal terga without median dorsal ridge | 11 |
11 | Supracoxal sclerites rounded or bluntly pointed ( |
15 |
– | Supracoxal sclerites sharply pointed ( |
12 |
12 | Anterior margin of head capsule distinctly thickened ( |
|
– | Anterior margin of head capsule not thickened; dorsal view of abdomen; posterolateral spines of abdomen small ( |
|
13 | Shape of gills 3-6 without emarginations | 14 |
– | Shape of gills 3-6 with emarginations ( |
|
14 | Dorsal view of abdomen as |
|
– | Dorsal view of abdomen as |
|
15 | Gills 7 slender and pointed ( |
|
– | Gills 7 usually rounded apically, never as long and narrow as above; setae on inner surface of tarsi either simple or fimbriate, never pectinate | 16 |
16 | Cerci bear spines as well as lateral bristles and segments of the cerci with stout spines alternate with those lacking such spines ( |
|
– | Cerci not as above ( |
|
17 | Body and head with indistinct large pale dots and markings dorsally | 18 |
– | Body and head with distinct large pale dots and markings dorsally ( |
19 |
18 | Gills 1 banana-shaped | |
– | Gills 1 symmetrically pointed ovaloid ( |
|
19 | Gills 7 unsymmetrically ovaloid, obtusely pointed apically | |
– | Gills 7 narrowly lanceolate ( |
Unknown.
Egg chorion of
Huai Khayeng stream (Thong Pha Phum district, Kanchanaburi province).
The larva of
The larva of
Unknown.
Unknown.
Nam Thob Ranger Station, Phu Luang Wildlife Sanctuary, Nam Thob stream (Loei province).
The larva of
Larvae of
Unknown.
Unknown.
Khun Kon Waterfall (Chiang Rai province).
The larva of
Unknown.
Unknown.
Region of Doi Inthanon (Chiang Mai province); alt 2000 m, III 1999; bottom sample (leg. R. Braasch).
In contrast tothe larva of
The larvae of
Boonsoong and Braasch (2010) misidentified this species as
Unknown.
Mae Chaem district, Doi Inthanon NP (Chiang Mai province);
The larva of
The larva of
Unknown.
Unknown.
Tak province, highway 1090, km 64.5, mountain creek, riffle and run habitats; limy, gravel; leaf packs, wood, secondary forest; 750 m asl, c
The larva of
Unknown.
Unknown.
Doi Inthanon NP (Chiang Mai province).
This species resembles
This species was described by
The genus
Mae Hong Son province, Chiang Mai province, Chiang Rai province, Loei province.
The larva of
Only one species of
The Southeast Asian genus
Unknown.
Unknown.
Doi Suthep, Chiang Mai province; Loei province; Soppong, Mae Hong Son province.
Only one species of
Three species of
Unknown. Its prospective penis (Fig. 14,
Chorionic pattern of geometrically arranged small KCTs covering the entire egg surface (
Mae Hong Son province, Mae Chaem district, Doi Inthanon NP, Doi Suthep NP (Chiang Mai province)
Larvae of
KCTs randomly scattered laterally and concentrated at both poles, although larger and numerous at the pole (
Widely distributed in many parts of Thai streams.
The combination of having a distinctly thickened anterior margin of the head capsule, long posterolateral spines on the abdomen, acutely pointed supracoxal spurs, and well-developed lamellae on gills 1 will distinguish
Only one species of
The heptageniid mayfly genus
Chorionic surface characterized by granular matrix, large KCTs randomly scattered on entire egg surface (
Mae Hong Son province, Chiang Mai province, Trat province.
The larva and adults of this species were described by
Unknown.
Nam Lang River, Soppong (Mae Hong Son province).
Larva without emarginations on gills 2–6, gill 7 lanceolate and rounded apically, pale dots and marks on abdomen as on
Both
A brief comment on the appropriate placement of
Unknown.
Nam Lang river, Soppong, Mae Hong Son province,
Larva is conspicuous due to emarginations on gills 2–6, gill 7 being narrowly lanceolate, the head without markings, and the body with paired paramedian spots on tergites 5–8, large median spot on 9, and three distantly arranged small spots at anterior margin of tergite 10.
The habitat of the single larva found was submerged roots of a tree standing at the river bank.
Three species of
General shape ovoid, both poles with large KCTs densely arranged (
Chaiyaphum province, Mae Hong Son province, Chiang Mai province.
Only one species of
Genus
Soldán and
Soldán and
Egg ovoid, chorionic surface with mesh-like reticular ridges of a hexagonal structure, evenly covered with KCTs (
Chiang Mai province, Chaiyaphum province.
The larvae of
Larvae of
The larva and adults of
The synonymization of
Unknown.
Ban Nam Tok (Chiang Rai province).
This species is found to be an inhabitant of fast flowing rivers in Vietnam.
The larva and adults of
Unknown.
Nam Tok Ban Du (Chiang Rai province).
Head with blurred spots at forward margin; gill 1 up-turned banana-shape, 3 smoothly triangular gills with obliquely attached projection.
The larvae of
Only adults of
Unknown.
Unknown.
Mae Sot district (Tak province).
The larva of
The larvae of
Only larva of
The egg chorion of
Phromlaeng stream (Chaiyaphum province); Yakraue stream (Petchabun province); Nam Lang river, Pangmapa/Soppong (Mae Hong Son province); Chiang Mai province.
Male of
Larvae of
Unknown.
Unknown.
Mae Sot district (Tak province).
The larvae of
The larvae of
Only larva of
Unknown.
Ban Nam Tok (Chiang Rai province); Nam Lang river, Soppong, Mae Hong Son province.
This species is unique in the genus because of its abdominal pigmentation: terga pale yellow medially and reddish laterally. The male genitalia have an obvious projection between the two lobes. The larvae of this species are larger and have more pale dots and marks on head and body than those of the other known species (Figs 7, 9, 10,
Larvae of
The larva and adults of
1 | KCTs absent ( |
|
− | KCTs present | 2 |
2 | Small KCTs densely concentrated at each pole, much larger KCTs equatorially ( |
|
− | KCTs not as above | 3 |
3 | Chorion tuberculate or with peg-like structures | 4 |
– | Chorion reticulate ( |
|
4 | Coils concentrated at one or both poles and evenly distributed about remainder of egg ( |
5 |
− | Coils never concentrated at poles; evenly distributed around entire egg ( |
7 |
5 | Coils concentrated at one pole; chorion surface with peg-like structure ( |
|
− | Coils concentrated at both poles; chorion surface tuberculate | 6 |
6 | Many microgranules densely scattered all over the surface of the chorion; micropyle border well defined by a thickened rim beset with tubercles ( |
|
− | Rounded tubercles are scattered all over the surface of the chorion; micropyle border not strongly thickened ( |
|
7 | Chorionic surface folded, with many densely scattered crenulated granules; small KCTs covering the entire egg surface ( |
|
− | Chorionic surface with many sizes of granular matrix; large KCTs randomly scattered ( |
In addition to basic taxonomic research, revision of unclear or poorly defined genera, and association of larval and adult stages by rearing, investigation priorities of the Thai
We are most grateful to our colleagues for assistance during field trips and in collecting specimens. We would like to thank Department of Zoology, Faculty of Science, Kasetsart University (Bangkok, Thailand) for facilities and assistance. Thanks to reviewers for helpful revisions and critical comments to earlier drafts of this manuscript.