Other Marine Midges

How can I distinguish Clunio?

Here is an overview and comparison of chironomids commonly found in marine habitats.
 

Clunio

• Distinct characters: Females wingless; males with very prominent hypopygium (pincers at the rear end), which is rotated by 180°; presence of adults is usually strongly rhythmic: adults can only be found at specific lunar phases (mostly around new or full moon) and on these days during one of the two low tides (usually the lower low tide, in case of unequal tides)
• Length: <3mm
• Male antennae: NOT feathered, usually 11 segments
• Movement: Glide on the water surface in long strides, often along the edges of rocks; walk on emerged algae; male carries female (see picture)
• Habitat: usually rocky intertidal, but also described for mud flats (Florida, Northern Norway) or open sea (Baltic Sea)
• Distribution: likely global
• More pictures on iNaturalist

---

Thalassosmittia

• Distinct characters: both sexes winged
• Length: <3mm
• Male antennae: feathered, with 10-14 segments
• Movement: in swarms of a dozen to several hundred midges at low tide in the intertidal in wind-protected sites (behind rocks, etc), about 20-100 cm above ground; sometimes standing on the water surface, but only moving very little and quite erratically (no long strides as in Clunio)
• Habitat: usually rocky intertidal
• Distribution: North America, Europe, Japan
• More pictures on iNaturalist

---

Pontomyia

• Distinct characters: males with reduced wings and long antennae; front anf hind legs very long and held in distinct position (see picture) for water gliding; females wingless, without antennae and with very much reduced legs
• Length: ~4 mm
• Male antennae: NOT feathered
• Movement: water gliding
• Distribution: Western Pacific, Australia
• More pictures on iNaturalist

---

Telmatogeton

• Distinct characters: long legs, wings fully developped in both sexes, hypopygium rotated by 180°C, palpi with 2 segments
• Length: ~5 mm
• Male antennae: NOT feathered, with 7 segments
• Movement: swiftly walk on rocks in the splash zone or in the exposed intertidal, also fly short stretches every now and then
• Distribution: likely global (considered invasive in some places)
• More pictures on iNaturalist

---

Thalassomya

• Distinct characters: very similar to Telmatogeton, but palpi with 4 segments
• Length: ~5 mm
• Male antennae: NOT feathered, with 7 segments
• Movement: similar to Telmatogeton
• Distribution: likely global, but records so far restricted between 60°N and 25°S
• More pictures on iNaturalist

---

 

There are also marine species in the genera Tanytarsus (or Yaetanytarsus), Chironomus, Halocladius, Kiefferulus, Dicrotendipes, Polypedilum and a couple more. Information on those will follow.