First record of water mite larvae, Hydrachna sp. (Acari, Hydrachnidae) parasitism as quiescent nymphophan on two major aquatic insects of Coleoptera and Hemiptera from West Bengal and Odisha, India

Occurrence of quiescent nymphophan of Hydrachna sp. attaching to the sternites and tergites of thorax and abdomen of water beetle (Hydrophilus sp.) and giant water bug (Lethocerus sp.) is reported for the first time from West Bengal and Odisha of India. After feeding from one to five weeks as a parasitic larva on its host, Hydrachna sp., stops feeding and enters a quiescent nymphophan (nymphochrysalid) stage of development in which the larva squeezes into its exoskeleton and forms a sac-like structure where metamorphosis occurs. By the means of gnathoma, it remains attached to the host body casts off its exoskeleton, and within a short time, the developing nymph can be seen within it. The nymph comes out of a slit in the exoskeleton and assumes a free-living existence. These nymphochrysalids ranged in length from 682.17 to 2112.45?m with lateral stripes adorning their external integuments. Body appeared to be bottle shaped with pointed or rounded posterior end. Preferences of water mites for insect host body parts and seasons, infection intensity and prevalence were reported.