I found this small Lesser Boatman species (3.5 millimeters) in a large pond. Cymatia coleoptrata can be found in regions that lie in a rather narrow band over Northern Europe, according to gbif.com. In the Netherlands and parts of Belgium it is quite common, the two other species which can be found there are the rather rare C. bonsdorffi and the very rare C. rogenhoferi) (B. Aukema, 2016). C. coleoptrata is the smallest of these three.
Unlike many other Lesser Waterboatman species, Cymatias are not bottom dwelling and detritus hoeing. Instead, according to many sources they seem to be hunters that dart for small creatures like moquito larvae, mayfly larvae and crustaceans, e.g. waterfleas (Hädicke et al 2018, see below).They grab them with their front legs, which are not shaped like e little shovel, but are cylindrical and have long, hairlike projections on them, to from a kind of cage trap.
Literature:
Hädicke C.W., Rédei D., & Kment P.(2017) The diversity of feeding habits recorded for
water boatmen (Heteroptera: Corixoidea) world-wide with implications for evaluating
information on the diet of aquatic insects Eur. J. Entomol. 114: 147�159, 2017
doi: 10.14411/eje.2017.020 Read it 5 april 2022 from http://www.eje.cz
Aukema, B. (2016) Nieuwe en interessante nederlandse wantsen VI (Nederlandse
Faunistische Mededelingen 46 - 2016)
Read it 4 april 2022, from https://repository.naturalis.nl/document/667945
Stoffelen, E., Henderickx, H., Vercauteren, T., Lock, K.,& Bosmans, R. (2013) De
water- en oppervlaktewantsen van Belgiië (Hemiptera, Heteroptera: Nepomorpha Gerromorpha)
Determinatiesleutels, beschrijvingen en foto's van de volwassen water- en
oppervlaktewantsen Koninklijk Belgisch Instituut voor Natuurwetenschappen, Brussel 2013
(ISBN: 9789073242272)
Read it 4 april 2022, from
http://biblio.naturalsciences.be/rbins-publications/faune-de-belgique-fauna-van-belgie/de-water-en-oppervlaktewantsen-van-belgie/water-en-oppervlaktewantsen-all.pdf