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On my walk around town today I found this small black bug, (keychain carabiner for scale).

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Closeup

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It has two antenna and it seems that there is white on the edge of the segments.

Does anyone know what kind of bug this is?

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  • DIIK, but it is either a bug that is essential to the local ecology or bug that hitchhiked on a shipment from elsewhere that is a disaster for the local ecology. In other words, an important question.
    – ab2
    May 18, 2019 at 22:05
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    Where are you from that you've never seen one of these? I thought they were ubiquitous. (Serious question)
    – msouth
    May 19, 2019 at 5:10
  • @msouth I have seen them before just thought I would ask what they are exactly
    – Charlie Brumbaugh
    May 19, 2019 at 5:18
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    I have about 5000 of them in my compost bin.
    – Eric Duminil
    May 19, 2019 at 20:35
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    OK gotcha, the question struck me as someone asking who'd never seen one before, which was amazing to me because I think I've seen them everywhere I've lived in the US. Did you know they breathe using gills? (I had four boys, we were trying to figure out how to keep them alive as "pets". Did not succeed at this but learned a bit about them :D ).
    – msouth
    May 19, 2019 at 20:49

3 Answers 3

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Probably a woodlouse which is a type of crustacean in the suborder Oniscidea.

enter image description here

Source: a-z animals

They are globally distributed, except in polar regions and arid deserts, and are also known by the following names:

  • "armadillo bug"
  • "boat-builder" (Newfoundland, Canada)
  • "butcher boy" or "butchy boy" (Australia,mostly around Melbourne)
  • "carpenter" or "cafner" (Newfoundland and Labrador, Canada)
  • "cheeselog" (Reading, England)
  • "cheesy bobs" (Guildford, England)
  • "cheesy bug" (North West Kent, England)
  • "chiggy pig" (Devon, England)
  • "chucky pig" (Devon, Gloucestershire, Herefordshire, England)
  • "doodlebug" (also used for the larva of an antlion)
  • "gramersow" (Cornwall, England)
  • "granny grey" (South Wales)
  • "hog-louse"
  • "monkey-peas" (Kent, England)
  • "monk's louse" (transl. "munkelus", Norway)
  • "pea bug" or "peasie-bug" (Kent, England)
  • "pill bug" (usually applied only to the genus Armadillidium)
  • "potato bug"
  • "roll up bug"
  • "roly-poly"
  • "sow bug"
  • "slater" (Scotland, Northern Ireland, New Zealand and Australia)
  • "wood bug" (British Columbia, Canada)

Source: Wikipedia

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  • I had no idea these had so many names and occupied so many regions of the world!
    – Radvylf Programs
    May 19, 2019 at 14:23
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    @RedwolfPrograms: maybe because the official name is terrible.
    – Joshua
    May 19, 2019 at 20:16
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    @Joshua I think you mean "lousy".
    – David Richerby
    May 19, 2019 at 21:54
  • The one in this photo seems to be a '78 model. The OP clearly posted a pre-'74 model.
    – dotancohen
    May 20, 2019 at 7:18
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I see these everywhere where I live (Central Texas). We usually call them "pill bugs" or "rollie-polies" (usu. young children).

It shouldn't do you or anything you own any harm; they mostly just crawl around on things and roll up into a ball when you touch them. Kids would always run around collecting them when I was in school.

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  • While I agree that these guys are not dangerous to people or pets, and are generally helpful in the garden, they will absolutely massacre any strawberries or plant seedlings they come across. Apparently they also ringbark seedlings
    – mcalex
    May 20, 2019 at 5:17
  • @mcalex Well, I'd expect this question was mostly about camping/hiking, and very few hikers carry seedlings or garden with them.
    – Radvylf Programs
    May 20, 2019 at 12:25
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This is a terrestrial isopod crustacean called a woodlouse (colloquially referred to as pill bugs, potato bugs, roly-pollies, sow bugs, etc.).

enter image description here

There are over 5000 species in the world with at least 64 in Russia (see Kuznetsova & Gongalsky 2012).

Habitat:

Woodlice are typically found in damp, dark places -- in the soil, under rocks/logs/debris, etc.

Living in a terrestrial environment, woodlice breathe through trachea-like lungs in their paddle-shaped hind legs (pleopods), called pleopodal lungs. Woodlice need moisture because they rapidly lose water by excretion and through their cuticle, and so are usually found in damp, dark places

Description:

As with all arthropods, the woodlouse is a segmented animal with a rigid exoskeleton and jointed limbs.

  • However, this is not an insect! Insects have 3 pairs of legs while isopods have 7 pairs of legs.

The extended uropods on your specimen as well as the pereon-pleon junction, number of antenna flagella, etc. all are important for IDing to species. (E.g., see here).

Note: although many people associate these arthropods with the ability to roll up into a perfect ball, only woodlice in the genus Armadillidium and in the family Armadillidae can roll up into an almost perfect sphere as a defensive mechanism.

Diet:

Woodlice are generally detritivores, meaning they eat decaying organic matter.

Citations:

Kuznetsova, Daria M., and Konstantin B. Gongalsky. "Cartographic analysis of woodlice fauna of the former USSR." ZooKeys 176 (2012): 1.

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