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From: Stephen Shaw <srshaw@Dal.Ca>
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Hi Dave et al,
Curious also, I checked cantharidin on Wikipedia, recalling having read somewhere that an entire French Foreign Legion outpost was reputedly immobilised, so to speak, from painful priapism of many hours duration from ingesting the stuff as Spanish Fly, intended as an aphrodisiac.   The LD(50) (the lethal dose estimated to kill 50% of those receiving it) is cited as 0.5mg/kg for humans, so for a modest 50kg/110 lb human, LD(50) would be 25 mg, but the text says that as little as 10 mg 'can be lethal' (or 'has been lethal'? - otherwise how would you know?).  Some blister beetle species (Epicauta) are said to contain nearly 5 mg each, so grinding up and ingesting an extract from as few as 2-5 such beetles could do you in.

For horses, 1 mg/kg is quoted.  Apparently, a few beetles hiding in bales of feed hay have made short work of some horses.  

Depending on whether it's a recent edition, one would normally rate the Merck Index above Wikipedia for reliable numbers, otherwise perhaps vice versa for some substances. 
Steve (Hfx) 
From: David & Alison Webster [dwebster@glinx.com]
Sent: Monday, October 5, 2015 8:59 PM
To: Jim Wolford; Ian Manning
Cc: Chris Majka; David McCorquodale; Angus MacLean; Stephen Shaw
Subject: Re: [New post] Blister Beetles’ Defense Mechanism

Hi All,
    I just noticed that this was not on Naturens so my reply a few minutes ago, effectively to Jim only, is pasted below.
 I wouldn't bet the farm on this being a balanced account.

     According to my Merck Index 9th ed., the subcutaneous LD in rabbits of cantharidin is 100 mg/Kg. Cantharides (Spanish Fly), derived from Cantharis vesicatoria [really Lytta vesicatoria DW], is stated to contain 0.6-1% cantharidin and to be highly toxic to humans by ingestion or absorption from skin or mucous membranes.

    I wonder if the reference, in this Naturally Curious article, to 100 mg being lethal to humans, originated in the 100 mg/Kg sc lethal dose of rabbits.
YT, DW, Kentville
----- Original Message -----
From: Jim Wolford<mailto:jimwolford@eastlink.ca>
To: Ian Manning<mailto:ianmanning4@gmail.com>
Cc: Chris Majka<mailto:c.majka@ns.sympatico.ca> ; David McCorquodale<mailto:david_mccorquodale@cbu.ca> ; Angus MacLean<mailto:angusmcl@ns.sympatico.ca> ; Stephen Shaw<mailto:srshaw@dal.ca> ; David & Alison Webster<mailto:dwebster@glinx.com>
Sent: Monday, October 05, 2015 6:04 PM
Subject: Re: [New post] Blister Beetles’ Defense Mechanism

Thanks, Ian!  OK to disseminate more widely?

On Oct 5, 2015, at 8:57 AM, Ian Manning <ianmanning4@gmail.com<mailto:ianmanning4@gmail.com>> wrote:

Another bite of cool natural history from Mary Holland.


---------- Forwarded message ----------
From: Naturally Curious with Mary Holland <comment-reply@wordpress.com<mailto:comment-reply@wordpress.com>>
Date: 5 October 2015 at 08:03
Subject: [New post] Blister Beetles’ Defense Mechanism
To: imanning@upei.ca<mailto:imanning@upei.ca>

Mary Holland posted: "Blister beetles are aptly named, for when they are disturbed they emit a yellow, oily, defensive secretion (cantharidin) from their joints which usually causes blisters when it comes in contact with skin. This toxin deters many potential predators and is "
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New post on Naturally Curious with Mary Holland
Blister Beetles’ Defense Mechanism<https://naturallycuriouswithmaryholland.wordpress.com/2015/10/05/blister-beetles-defense-mechanism/>
by Mary Holland<https://naturallycuriouswithmaryholland.wordpress.com/author/naturallycuriouswithmaryholland/>

[10-5 short-winged blister beetle 064]<https://naturallycuriouswithmaryholland.files.wordpress.com/2015/10/10-5-short-winged-blister-beetle-0641.jpg>Blister beetles are aptly named, for when they are disturbed they emit a yellow, oily, defensive secretion (cantharidin) from their joints which usually causes blisters when it comes in contact with skin. This toxin deters many potential predators and is especially effective against ants. According to naturalist/forester/writer Ginny Barlow, as little as 100 milligrams is reported to be fatal to humans if ingested, and this amount can be extracted from just a few beetles. Humans used to crush and dry blister beetles and use the resulting concoction for gout and arthritis. It was also used as a popular aphrodisiac known as Spanish fly. Because of its toxicity, it is no longer widely used in medicine.

Cantharidin is, however, indirectly used by tree-nesting nuthatches. With a limited number of tree cavities, there is competition among animals using them to raise their young, especially between squirrels and nuthatches. Nuthatches have been seen with Short-winged Blister Beetles (Meloe angusticollis, see photo) in their beaks, "sweeping" them on the bark around tree cavity entrances. The nuthatches don’t eat the beetles, they strictly use them as tools. It is assumed that the birds do this in order to repel squirrels with the cantharidin that is smeared on the tree. (Thanks to Ginny Barlow for photo opportunity.)

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com<http://www.naturallycuriouswithmaryholland.wordpress.com/> and click on the yellow “donate” button.

Mary Holland<https://naturallycuriouswithmaryholland.wordpress.com/author/naturallycuriouswithmaryholland/> | October 5, 2015 at 7:01 am | Tags: Cantharidin<https://naturallycuriouswithmaryholland.wordpress.com/tag/cantharidin/>, Meloe angusticollis<https://naturallycuriouswithmaryholland.wordpress.com/tag/meloe-angusticollis/> | Categories: Beetles<https://naturallycuriouswithmaryholland.wordpress.com/category/beetles/>, Defense Mechanisms<https://naturallycuriouswithmaryholland.wordpress.com/category/defense-mechanisms/>, Insects<https://naturallycuriouswithmaryholland.wordpress.com/category/insects/>, October<https://naturallycuriouswithmaryholland.wordpress.com/category/october/>, Short-winged Blister Beetle<https://naturallycuriouswithmaryholland.wordpress.com/category/short-winged-blister-beetle/>, Uncategorized<https://naturallycuriouswithmaryholland.wordpress.com/category/uncategorized/> | URL: http://wp.me/pNTN1-35w

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