_ spp. in >30 genera of 8 families in our area; worldwide, ~1,200 spp. in 113 genera of 10 families, arranged into 5 superfamilies (one small Neotropical family and one monotypic family restricted to Canary Is. are not represented in our area)(1)
Abdominal segmentation dorsally indistinct. Antennae longer than head. Body size usually >0.7 mm. Eyes usually present. Trunk distinctly subglobular, terminated by a much smaller unit.(1)
In Symphypleona, the eversible sacs of the ventral tube have evolved into long multifunctional tubes, used [i] to regulate the internal osmotic pressure by taking up water with the tips of the eversed sacs/tubes, [ii] to adhere to smooth surfaces, and [iii] for grooming. (From Frans Janssens's comment)
In Symphypleona, the eversible sacs on the ventral tube have evolved into long tubes used to regulate the internal osmotic pressure (tube tips can take up water) and to adhere to smooth surfaces, and also for grooming. --Frans Janssens
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