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I'm not even sure it's an insect: the best I can do is identify it as an arthropod. I captured this slow-moving organism and after a period of observation under high magnification, I concluded that it appears to construct a "shell" from miscellaneous particles or debris. With a scalpel, I carefully cut this outer casing open to observe the organism, and the pictures show what I found. It seems to have six legs, like an insect, but is oddly worm-like and wingless. Total length is approximately 1 cm. I do not believe that this is a juvenile/larval/instar form. I've seen several of these where I live, and they always look like this (with maybe a +/- 20% size variation).


Edit: This specimen was found in San Diego County, California, United States.

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    $\begingroup$ Closely related question/answer: biology.stackexchange.com/questions/15845/what-insect-is-this/… $\endgroup$ – fileunderwater Jan 23 '17 at 12:53
  • $\begingroup$ We have a lot of these in our house. $\endgroup$ – Gene Jan 23 '17 at 15:12
  • $\begingroup$ We have a ton of these in our garage! (Los Angeles) Thanks so much for asking, I've always been curious about them. $\endgroup$ – Lindsey D Jan 23 '17 at 18:11
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    $\begingroup$ These case building moths have shown up a few times on this site. Hands down, though, these are the best pictures. $\endgroup$ – theforestecologist Jan 24 '17 at 21:11
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It is the larva of household casebearer moth (a Lepidoptera), named after the larval stage. It is scientifically called Phereoeca uterella.

It is found through out South and North America.

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The larva constructs a protective case from silk and camouflages it with other materials such as soil, sand and insect droppings.

References:


Further reading: Household Casebearer, Phereoeca uterella by Juan A. Villanueva-Jimenez and Thomas R. Fasulo

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    $\begingroup$ so does cutting off it's shell (like the OP did) harm it? Or can it just grow another shell? $\endgroup$ – user17915 Jan 23 '17 at 12:41
  • $\begingroup$ @user17915 There is no scientific work on the impact of removal of the larva from its case but I think it does affect the larva if done so because there must be a real significance behind spending a lot of energy synthesising the threads of the case which begins even before the larva hatches out. $\endgroup$ – Tyto alba Jan 23 '17 at 17:30

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