Wooly Bears

[Richard Worth]

Hey all,
I too have been rearing wooly bears.  Right now they are in winter 
diapause but it is warming up a little and I need to find a source of 
food.  I was rearing them on willow but may have to go to dandelions 
or something.  They were brought to me as eggs and I had no idea what 
they were (other than arctiid) until they got big enough.  This was 
more just an exercise in trying to get them to overwinter than 
studying band width.  So far only the smallest have died.  I keep 
them moist and in the cool garage like they would be if outside. 
Last summer they ate like pigs and grew enormous.  They started out 
all black and by diapause were about 1/3 orange.  So far it does 
appear that the band gets wider at each molt.  I also had to let 
about half of them go but still have about 60.  I will pay close 
attention to band width as they finish development and see if those 
with the widest bands become females.
Happy collecting,  Rich

>I've been interested in what influences the width of the orange band in
>Wooly Bear larvae (_Pyrrharctia_isabella_) and have some casual
>observations to offer in the hope that others might have additional
>information, data or references to contribute. A few years ago I did a
>casual literature search and couldn't find much of anything on the factors
>that influence band width. Just general statements to the effect that the
>width of the band varys with instar -- nothing quantified or very specific,
>just remarks that suggested it might be "common knowledge" or unattributed
>observations passed on from one entomological generation to another.
>
>I decided to see if there was any genetic influence on band width and
>thought I'd raise some Wooly Bears and, if there was any variation, attempt
>to establish lines of narrow-banded and broad-banded moths by inbreeding.
>I've been frustrated in accomplishing that goal, but I've made some
>observations that might be of interest to the list.
>
>First, the extent of the orange band does vary with instar. I started out
>with over 300 larvae from a single female and soon couldn't manage all of
>them. I reduced them to two dozen by selecting 12 with the narrowest and 12
>with the broadest bands. I released the others into the wilds of my
>backyard. Now the strange thing happened. As the remaining 24 grew and
>molted the extent of the orange band increased in both groups until most of
>them were just one big orange band. Some had a little tuft of black on the
>front, but most were completely orange. Unfortunately I also had shifted
>the larvae to a new food plant at this time, so I don't know if the change
>was due the age or the new food. (I ran out of the broad-leaf plantain I
>was using and started feeding them on wild blackberry. I actually tried a
>number of species, but they seemed to prefer the blackberry in a
>taste-choice test.) Later instars regained their black ends and started
>looking more like standard wooly bears, but the completely orange phenotype
>persisted throught a couple of molts.
>
>I lost this group of larvae when I attempted to overwinter them.
>
>The next year I got another batch of w.b. larvae started earlier in the
>summer and they pupated in July. These had also been all orange. I eagerly
>awaited their emergence so I could mate them and get a sibship line going,
>but all the moths were female! Twice I have selected the larvae that have
>the most orange in one of the earlier instars and the resulting moths have
>been all female.
>
>I wish now that I had kept more detailed notes -- I know better, but this
>was a casual project that I hadn't devoted a lot of thought or attention
>to. I hope to pursue it again this summer more carefully.
>
>Again, if any of you have references or know of studies on the factors that
>influence the width of the band in these caterpillars I'd appreciate
>hearing from you.
>
>Cheers!
>
>Dale Hoyt
>
>
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Richard A. Worth
Oregon Department of Agriculture
Plant Division
rworth at oda.state.or.us
(503) 986-6461

 
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