Scuds and Cress bugs

[TimRobinsin]

Was out on a spring creek recently and it reminded me of a question I have yet to answer.

Why do scuds change colors?

I have heard many stories about this ranging from habitat to life cycle. I have seen scuds in this stream vary in color through out the year. Colors observed include: white, olive, gray, blueish, orange, tan and pink. I have looked on trout nut and google. I just thought I would throw it out there if there are any biologists in the know one here.

also, it seems like cress or sow bugs do the same to some extent.

Just a fun question. I had a great time catching on cress bugs. BIG cress bugs, size 12 - 10. The cress bugs were all over every piece of aquatic vegetation in every type of water (fast, slow, riffle, still)

it's that time of year. the fish are willing.

 

[LetortAngler]

"Why do scuds change colors?"

If you had a scud that lives in a bed of dark green watercress, the scud will give off a darker green color due to the watercress being the primary food source. Scuds are transparent, therefore what they consume will reflect their color. Some scuds have parasites in their intestinal tracts which gives them that small orange dot that many scud patterns out there try to replicate, as with pregnant scuds.
The white and orange scuds are likely dead scuds, I've never seen a completely white or orange one that was alive, but trout of course will key on the easy picking of those that do not camouflage into the background.
Hopefully some others can chime in.

 

[Fishidiot]

Interesting.

I've spent a lot of time looking at scuds and cress bugs and have not noted such a great color variation, although perhaps I've not been looking carefully enough. Most of the (live) scuds here in the CV are in the olive range and cress bugs in the olive/gray range.

 

[TimRobinsin]

so I went back to my stream and I would say half of the cress bugs are gone but the ones that are still there are HUGE! easily size 10.