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Weevil-thigh Lice

What on earth are these invertebrates?!? I haven’t got a clue – a situation which is exciting and frustrating in equal measures!

mystery invertebrate (in DMHF)

mystery invertebrate in situ on the right hind-femur of the weevil Sitona lepidus

I found four specimens on Wednesday from a wetland site on the edge of Pevensey Levels, East Sussex. I didn’t see any in the field but started noticing them as I was identifying my beetle specimens. The first was loose in a tube with two Datonychus melanostictus and I assumed it was bycatch, rather than a parasite of the weevils. But I then found one attached by its mouthparts to the mid-femur of a Protapion fulvipes, and two more attached to the hind femur of a Sitona lepidus.

I don’t think these things can be common or I’d have noticed them before. Maybe I’ve seen them before with eyes blinkered to all but beetles and just disregarded them? For the time being I will call them Weevil-thigh Lice. I would dearly like to give them a scientific name and unlock whatever knowledge exists about them. But the only way I can think to go about identifying them is to stick the photos up here and ask – do you know what they are?


  1. hans-erik wanntorp says:

    mite juveniles

  2. markgtelfer says:

    It is a juvenile mite of some sort. Thanks to Brian Nelson and Joe Parker for the ID.

  3. markgtelfer says:

    And thanks to Hans-Erik too!

  4. markgtelfer says:

    Dr Anne Baker of the Natural History Museum emailed within a few days of my blog post with the following information: “Your specimens are indeed immature mites. They are six-legged larvae belonging to a member of the family Erythraeidae (suborder Prostigmata) – the most likely genus is Leptus. The majority of erythraeid larvae are parasitic, using a variety of insects and arachnids as hosts. After feeding, the larvae drop to the ground to complete their life cycle. The protonymph and tritonymph (first and third nymphs) are inactive, non-feeding developmental stages. The deutonymph and adults are free-living in, for example, soil, leaf litter and the aerial parts of vegetation. They are mostly predators of small arthropods, but some are evidently pollen-feeders.”

  5. markgtelfer says:

    I also heard from Owen Seeman of the Queensland Museum, South Brisbane, who emailed via Chris Reid to say: “That animal is the larva of an Erythraeidae, a type of mite that has a larva parasitic on terrestrial arthropods, then free-living life stages. Those flask-shaped mouthparts are fairly distinctive of the genus Leptus, which is a cosmopolitan genus with lots of species, but I wouldn’t commit to an identification without putting one on a slide. They’re not very host-specific: it wouldn’t be surprising to find the same species on all sorts of beetles (but not on other orders, but it’s still possible).

    They belong to a higher group known as the Parasitengonina. One major radiation are the water mites (larvae on aquatic insects, nymphs and adults in fresh water); another are the chiggers (larvae parasitic on vertebrates, some transmit disease organisms). There are several families that parasitise insects. Adults with a pelage of red setae are commonly known as red-velvet mites (usually Trombiculidae and Trombidiidae).”.

  6. Bob Marsh says:

    I am at this moment looking at a specimen of Sitona lepidus under the microscope. This has a specimen of the mite adhering to the left elytron, near the apex. The mite is pale yellow in colour and about 0.65mm in length. The first time I’ve ever noticed this mite on any beetle. I’ll put it down provisionally as Leptus sp.

  7. markgtelfer says:

    Thanks Bob, good to know of another record from Sitona lepidus and that it’s not just me who’s never seen/noticed these before.

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