Time's fun when you're having flies

South American madicolous midges

Niphta brunnea Pivar [PI-VAR] a tiny fly less than 2 mm in length, is one of nine new species from South America that are rewriting what entomologists understand about of larval morphology and microhabitats of the little-known family Thaumaleidae.  In spite of being rarely collected, the family has several common names: solitary midges, trickle midges, or madicolous midges.

The family includes about 200 species widely distributed around the world.  Most known species live in Europe and North America, but recent work is adding species from other regions, especially the southern hemisphere.

Madicolous midges are small, from 1.5 to 5 mm in length, yellowish to dark brown in color, with stocky bodies.  They belong to the superfamily of flies that includes black flies, biting midges or no-see-ums, as well as non-biting midges or chironomids.  Some believe them to be the closest relatives to black flies, but unlike black flies they do not feed on mammalian blood and do not vector disease.

Habitat and immatures of members of the Niphta nudipennis group A type locality of N. brunnea sp. nov. and N. daniellae sp. nov., box indicating where plant stem in images B, C was taken from (38°14'20.6"S 71°53'46.6"W) B larvae of N. brunnea sp. nov. on plant stem from splash zone C close up of N. brunnea sp. nov. larva, adhesive structure visibly in contact with substrate D habitat of N. nudipennis, box indicating foliage in splash zone where immatures were found E pupa of N. nudipennis affixed to leaf with final instar larval exuviae visible. Source: Pivar, Sinclair & Moulton (2021).

The word madicolous refers to the fascinating, specialized places where these midges live.  Madicolous habitats exist where a thin film of flowing water covers a substrate, generally rock.  Examples can be found at the margins of waterfalls, in the splash zone of cascading streams, on rock-face seepages.  Larvae of madicolous midges cling to such surfaces, sometimes vertical rock faces, in spite of being occasionally washed over by debris.  This very particular microhabitat was first pointed out by Thienemann when he observed caddisfly larvae in central Europe.  He called it hygropetrishen or, in English, hygropetric.  We’ll stick with the currently popular madicolous.

Niphta brunnea was described in a revision of the genus by Robert Pivar, Bradley Sinclair and John Moulton.  Their work increased the number of South American species in the genus from 2 to 11, and for the family from 8 to 17.   It uncovered both an unsuspected microhabitat for the family and a surprising new morphological structure in larvae.  So far, most South American species have been collected in the far south, in Chile and Argentina, but more species remain to be discovered.  The first species from Brazil was only reported in 2018 and there is an undescribed species from Ecuador that is the northernmost limit for a South American species.  North American species extend southward as far as Mexico, but no species are known from Central America.  The genus Niphta also includes three species in Australia.  Such groups with species in South America whose nearest relatives are in Australia or South Africa, instead of the closer North America, provided early evidence leading geologists to the discovery of plate tectonics.  Niphta species follow the Andes, with larger numbers known as one proceeds southward, but the extent to which this is an artifact of collecting is not yet certain.  Additional exploration in South America will fill gaps in the diversity and geography of the genus.

Scanning electron micrographs of ventral view of larvae of Niphta brunnea sp. Nov. (A) habitus. (B) head and thoracic segments I&II. (C) thoracic segments II&III and abdominal segment I. (D) abdominal segments II&III. € abdominal segments VI-IX.  Abbreviations: A-abdominal segment; T-thoracic segment.  Scale bars = 1.0 mm.  Source:  Pivar, Sinclair & Moulton (2021).

Immatures of this and other South American species of the genus have ventral adhesive structures resembling suction cups.  Instead of being found on rock surfaces, they were consistently found on wetted vegetation in splash zones.  They cling to both living and dead plant material, including smooth leaves, herbaceous stems and ferns.   They can be located on the upper or lower surface of leaves, depending on which is being wetted.  The vegetation was not in the direct path of flowing water, but situated where it was splashed consistently enough to remain moist.  This association with vegetation expands known habitats for the family and these impressive suction cups are an entirely new morphotype for the family.  These plant-associated species differ in behavior from other members of the family.  Typically, they use quick sidewinding movements to escape predation.  Chilean Niphta were observed to be much slower, caterpillar-like in their movements which were slow and undulating.  The authors noted that these impressive adhesive devices were present eventhough larvae were never observed in high flow splash zones, speculating that they might be left-overs from an ancestor or perhaps their habitat is subjected to torrential water following heavy rainfall.  Interestingly, the larvae of the Australian species Niphta collessi do not have the adhesive pads.  Like all good science, these discoveries raise more questions than they answer.

Given their obscure habits, small size, and very specific habitats, it is not surprising that madicolous midges are rarely encountered by general insect collectors.  As specialists continue to search them out, however, there will no doubt be many adjustments to our understanding of their morphology, natural history, and geographic distribution.

Acknowledgment

I thank Dr. Bradley J. Sinclair for permission to reproduce the images.

Further Reading

Pivar, R.J., Sinclair, B.J., and J.K. Moulton (2021) Revision of the genus Niphta (Diptera, Thaumaleidae) Theischinger of South America, with descriptions of nine new species and a new immature morphotype.  ZooKeys 1063: 49-104.

Sinclair, B.J., Pivar, R.J., and Paul H. Arnaud, Jr. (2022) World catalogue of the family Thaumaleidae (Diptera: Culicomorpha). ZooTaxa 5225: 1-66.