Scarlet-bodied Wasp Moth (Cosmosoma myrodora) - way cool biology!

Mike Quinn entomike at
Wed Nov 1 15:49:50 EST 2006

Scarlet-bodied Wasp Moth (Cosmosoma myrodora) - NABA-SoTX

TX: Calhoun Co
Port O'Connor
25 - X - 2006
Petra Hockey

This insect's biology is as fascinating as the adults are beautiful...

Conner, W.E , R. Boada, F.C. Schroeder., A. Gonzàlez, J. Meinwald, & T.
Eisner. 2001. Chemical defense: bestowal of a nuptial alkaloidal garment by
a male moth upon its mate. Proceedings of the National Academy of Sciences




Moth Photographers Group



The moth occurs along the southeastern U.S. coast from Texas to Florida.

NBII (formerly USGS) photo and (incomplete) range map:

Climbing Hempweed, the caterpillar food plant, is wide ranging primarily
from central Texas eastward. Dogfennel Eupatorium, an important adult food
plant, is more narrowly dispersed and may account for the narrow
distribution of the moth in Texas.


Climbing Hempweed (Mikania scandens) - pix, TX range by region

Dogfennel Eupatorium (Eupatorium capillifolium) - pix, TX range by region



These moths display warning coloration, yet the caterpillars host on
non-toxic Climbing Hempweed, Mikania scandens, (family Asteraceae), a weedy
vine at field margins and roadsides that can completely obscure bushes and
small trees. The male moth extracts toxins known as "Pyrrolizidine
alkaloids" (or PAs) from Dogfennel Eupatorium (Eupatorium capillifolium) and
showers these toxins (Fig. 1B) over the female on filaments (Fig. 2) prior
to mating and also passes more alkaloids to the female during insemination.
The female in turn transfers some of the alkaloids to the eggs during

Fig. 1, B: the male (Left) has just ejected PAs, which are visible as a
diffuse misty cloud.

Fig. 2, SEM of filaments laden with PAs.

Conner et al. (2001) report that, "Although paternal contribution to egg
defense had previously been demonstrated for several arctiid moths,
protective nuptial festooning of a female by its mate, such as is practiced
by C. myrodora, appears to be without parallel among insects."



The filaments are termed flocculent:

The Flocculent. When we prodded open the ventral pouches of a male, the
flocculent, which is ordinarily densely packed within, tended to bulge out.
Further prodding may cause clusters of filaments to break loose and to float
away on air. The filaments tend to stick to foreign objects, but they
readily separate from one another. To effect their mass expulsion, the male
presumably needs do no more than partially evert the pouches by compressing
them from within.

Anatomically, the filaments may represent modified scales. Indeed, the
cuticular membrane lining the pouches bears pores (Fig. 2E) that may be the
openings of the sockets in which the filaments were originally implanted.

The filaments are elaborately structured (Fig. 2 A-D). Flattened rather than
cylindrical, and highly sculpted, they seem to be built for lightness,
flexibility, and strength. The sculpting also ensures that a vast surface is
provided for dissemination of the alkaloid.



"Field-collected moths were obtained at the Archbold Station [FL] by baiting
with air-dried roots of Eupatorium capillifolium (Asteraceae), a plant that
we found to contain pyrrolizidine alkaloids. We had previously noted
Cosmosoma to be attracted to such bait. The roots were hung in clusters,
about 1.5 m above the ground, and were kept moistened. They were inspected
intermittently throughout the night for visiting Cosmosoma that had alighted
on them."


Cosmosoma is not alone among Arctiidae in possessing male abdominal pouches
laden with flocculent. Such structures have been noted in a number of
species of Cosmosoma, all members of the tribe Euchromiini, in which the
pouches may even have evolved more than once (17). No function has been
demonstrated for the pouches, although an interesting observation suggests
they may at times be used for defense. Even slight manual disturbance is
said to result in forceful expulsion of flocculent in some species (18). We
never noted our Cosmosoma to respond in such fashion.

Nor is Cosmosoma alone among arctiids in being attracted to pyrrolizidine
alkaloids or pyrrolizidine alkaloid-containing plants (19, 20). Alkaloid
sequestration, for protective purposes as in Cosmosoma, is therefore likely
to occur in other species as well.


Cosmosoma festivum - recorded 1x s. TX, s. FL

C. festivum - photo

Other species of Cosmosoma south of the border:

A different arctiid (Cisseps fulvicollis) on Eupatorium, no doubt also
collecting PAs...


Conner et al. (2001) briefly mention that Danaus gilippus also use PAs.

Queens (Danaus gilippus) require PAs for courtship as well, but in this case
the PAs are converted to pheromones rather than protective chemicals. (If I
had known there was this fascinating world of plant-insect interaction
chemistry, I might have paid more attention during Organic Chemistry...)

Multiple male Queens on withered Eupatorium greggii

Boppré (1979) apparently found that withered or damaged plants in the tribes
Senecioneae and Eupatorieae of the Asteraceae, as well as plants in the
Boraginaceae and Fabaceae were particularly attractive to male danaids.

Boppré, M. 1979. Lepidoptera and withered plants. Antenna (Bulletin of the
Royal Entomological Society of London 3: 7-9.

Multiple male Queens on Senecio riddelli

Multiple male Queens on Senecio confusis

Male Queen shown with extruded hairpencils releasing pheromones in front of
a female Queen:

Mike Quinn, Austin
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