Isopods acting strange and dying off (Porcellio Laevis Dairy Cows)
Warning: close up pictures of dead and decayed isopods
I have had this Dairy Cow colony for over a year at this point, and have experienced occasional die-offs due to moisture or substrate issues, but otherwise everything has been relatively normal. Recently however, some isopods have been sluggish (falling off things, moving slowly), dying on the dry side of the enclosure, or glass surfing for unusually long periods of time. I figured it was a moisture or other simple issue but then I saw an isopod die and within two days it had decomposed significantly.
I'm not sure what has caused this, they seem to crowd in a huge group on the moist side which always makes me think there isn't enough moisture. I live in an extremely dry place so I water them every day with distilled water, otherwise die-offs occur. Additionally, we placed some of this year's sunflowers inside (they seem to like to eat those) which may have introduced some kind of bacteria?
The same isopods that glass surf appear to be thin and often have small black spots on them. I managed to catch this one to take close pictures of it, and you can see unnatural coloration on the bottom (on healthy isopods it seems to be a milky white-yellowish color all over). It is also unusually thin, though I'm not sure if this is captured in the pictures.
This gravid female, which I did not handle, also appeared to have a black spot on its pouch.
Sometimes these marks are hard to distinguish from the natural black-spotted coloration of Dairy Cows, but when it appears on the bottom of the isopod it is conspicuous. Here is the dead individual mentioned at the start of the post, which rotted far quicker than is typical. It has only been dead for maybe two days.
Note the dark brown coloration along the bottom of the isopod. Normally, when an isopod dies of something like dehydration, it appears a dark yellow. I have only seen this type of coloration when the isopod is overly moist, but this one was found in a dry area.
Other dead individuals afflicted by this condition appear similarly, with this dark brown coloration, sometimes in spots, appearing in bone-dry areas of the enclosure. Additionally, some of them appear almost "stuck" when glass surfing, like they can't get past an obstacle. Weirdly, this is an obstacle that other isopods evidently can get over, which implies they are very weak or disoriented. I sometimes find them dead in the same place, or nearby if I make an attempt to move them from that spot. Here are some other pictures of similar dead individuals, to provide a larger sample size.
This has been very distressing to me, and the colony is so large and the symptoms so hard to see that quarantining all of the afflicted isopods may be nearly impossible. I have even seen this on juveniles, though I wasn't able to capture any for these pictures. Any information is appreciated.
Posted Dec 1, 2025, 5:50 PM UTC