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2019-08-25

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The combination of hydrophobic setae(bristles) on their legs and water surface tension prevents the bugs from sinking.  

Scientists of the Zoological Survey of India have discovered seven species of water treaders, semi-aquatic insects that can walk or run on the surface of water.

The newly described species belong to the genus Mesovelia whose size ranges from 1.5 mm to 4.5 mm and are equipped with hydrophobic setae (bristles) on their legs. The combination of hydrophobic setae and water surface tension prevents them from sinking. The insects are pale green with silver-white wings with black veins on the basal half which make them stand out over the green mat of aquatic weeds. Among the new discoveries, Mesovelia andamana is from Andaman Islands, M. bispinosa and M. isiasi are from Meghalaya, M. occulta and M. tenuia from Tamil Nadu and M. brevia and M. dilatata live both in Meghalaya and Tamil Nadu.

The details of the discovery were published in a paper in the journal Zootaxa earlier this month.

“These bugs are hemimetabolous insects without having larval stage i.e., they go from egg to nymph to adult. They are found on freshwater bodies such as ponds, lakes, pools, streams, rocks with moss and sometimes on estuaries,” E. Eyarin Jehamalar, one of the authors of the paper, said.

Ms. Jehamalar said these bugs serve as predators and scavengers (feed on midges, water fleas, feed on dead and dying mosquitoes), thereby removing organic waste and also providing a natural sanitation service. The females of Mesovelia are larger than males and dig several holes on plants and insert eggs in plant tissues with a specially adapted long serrated ovipositor (genital organ).

There are 12 species of genus Mesovelia found in the country. While large water striders (Limnogonus, Aquarius, Cylindrostethus, Gerris, Ptilomera) are easily spotted upon the surface of water, the tiny Mesovelia are not as well-known.

Other than the size, there are morphological features that make these pond-weed insects different from water striders. The claws of Mesovelia are placed apically (tip or extreme end of legs), whereas in water striders, they arise from the pre-apex (just before the tip) of legs.

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