Mutated Monarch Part 2

Paul Cherubini paulcher at concentric.net
Thu Sep 30 06:42:30 EDT 1999


EE wrote:

> The Monarch eggs were collected around Aug. 8th from a vacant field
> across the train tracks from a golf course. They were kept in a newly
> built small outdoor enclosure that consisted of a frame made from wooden
> 1x1's covered with screening material. They were fed on milkweed from
> the field. 

Was the milkweed changed twice a day? Changing it only once a day seems
to  lead to nutritional and hydrational inadequacies -especially in the
later instars - that also seem to make the caterpillars more prone to
viral, bacterial diseases or protozoan parasites.

> The abdomen sticking out was green in colour.
> the butterfly wiggled a bit, but died within a few hours

Here in California we called this "green butt" disease. The green butt
is a symptom of a heavy infestation of protozoan parasite. However it's
possible there could be other conditions that cause it other than the
parasite - the parasite is fairly rare in eastern monarchs.

> On September 17th, the 10th caterpillar, the last to pupate, emerged. I
> After 4 hours, he flapped off ... not incredibly
> vigorously ... but he did fly off.

Again this sounds like a protozoan parasite - normal looking, but
smallish, and slightly weak and lethargic adults is a symptom of a
heavy, but not  lethal infestation.  Surprizingly, studies indicate many
of these heavily infected adults manage to lead normal lives.

> I've learned that most golf courses around here spray fungicides and
> imidacloprid (Merit).. Could the persistant pesticide or fungicide used to     > keep the greens mold free have caused the problem? Could it have been
> pesticides from the lawn chem truck which was also around one afternoon 
> spraying a lawn a half a block away? 

Not likely. Merit kills within a day if bugs receive a lethal dose.
Insects that receive sublethal doses have mixed function oxidases in
their guts that can rapidly detoxify many insecticides. 

Some of California's largest and most persistent monarch butterfly
overwintering sites are located on golf courses that are treated with
insecticides, fungicides and broadleaf weed herbicides. The butterflies
frequently bask, mate and drink dew water off these lawns. No one has
ever noticed this causes a problem for them. In fact, the two longest
lived tagged monarchs in recorded history (after tagging 1,000,000+
monarchs over the past 45 years by 1000 + people) were both tagged at a
golf course overwintering site where the butterflies cluster on exotic
Australian eucalyptus trees located in an urban area between Oakland and
San Jose, California. This evidence doesn't quite fit the popular
romanticized notion that monarchs require a pristine, all natural,
unaltered by man, sacred kind of overwintering sanctuary.

Paul Cherubini, Placerville, California


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