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to bobklips.com, the website of Bob Klips, a plant enthusiast living in
Columbus, Ohio.
Nipped in the bud!
(Japanese beetles munch rose mallow flowers)
Stage's Pond State Nature Preserve
Pickaway County, Ohio. September 2, 2008
A few of the rose-mallow (Hibiscus moscheutos,
family Malvaceae) flowers at Stage's Pond display oddly symmetrical
damage to their petals, no doubt inflicted by the Japanese beetle. The day before bloming, rose-mallow flower buds are exerted
from the protective calyx. The striking damage pattern is evidentally attributable to a
beetle's feeding during this late bud stage, when the petals overlap.
Nipped bud, and partly eaten rose-mallow flower
September 2, 2008, Stage's Pond Stage Nature Preserve, Pickaway County, Ohio.
Rose-mallow and the hibiscus bee
(Hibiscus moscheutos and Ptilothrix
bombiformis)
Stage's Pond State Nature Preserve
Pickaway County, Ohio. August, 2008.
Stage's Pond is an
isolated pond system
formed 17,000 years ago by water that plunged off the edge of the ice
sheet covering the landscape. Most of one pond, and
all of a second smaller pond, along with approx. 150 acres of wetland,
meadow and woods together comprise the Stage's Pond State Nature
Preserve. Stage's is a terrific natural area administered by the ODNR's
Division of Natural Areas and Preserves. It is approx. 30 miles
s. of Columbus, in Pickaway County.
Here's an aerial view. The yellow box is where we are.
Stages Pond, aerial view, from Google Maps. The yellow box includes a
portion of the rose-mallow population and the
nesting site for its principal pollinator, the hibiscus bee (Ptilothrixbombiformis).
Portions of the pond
margins and
considerable areas adjacent to it are densely occupied by a robust
herbaceous perennial marsh plant, common rose-mallow (Hibiscus
moscheutos, family Malvaceae).
Shoreline of Stage's Pond (3-picture panorama) August 4, 2008.
Typically, each
rose-mallow flower blooms
for one day. The plant below shows one perky-looking current
flower, and a drooping other one that bloomed the preceeding
day.
Common rose-mallow, Stage's Pond State Nature Preserve,
Pickaway County, Ohio, August 14, 2008.
At
Stage's Pond, rose mallow flowers occur in an intriguing variety
of colors (uniform within each plant but differing among
plants).
They can be white or pink (of various intensity), and
either with
or without a red center.
Rose-mallow flowers, showing variability at Stages Pond, August 18,
2008.
The principal
rose-mallow pollinator is the "hibiscus bee," Ptilothrix
bombiformis (family Anthophoridae), shown below in the
process of gathering pollen to provision her nest. Pollen
is combed off the anthers and carried on a ridge of long hairs along
each hind leg that is termed the "scopa." The scopa
(scopae?) seen here are so full of pollen they
resemble
bulging saddlebags.
Ptilothrix bombiformis gathering pollen (and
depositing some as well).
August 14, 2008. Stage's Pond, Pickaway County, Ohio.
Here'a a fuzzy little
YouTube video of Ptilothrix foraging on a hibiscus
flower for nectar
and pollen.
Ptilothrix is a solitary, i.e., non-social,
bee. As
such,
there is no division into reproductive queen/sterile worker castes as
occurs in honeybees and bumblebees. Instead, all the females
are
presumably reproductive. Their nests are placed
in hard-packed
soil in open areas situated fairly close to both rose mallows
and
open water. Here at Stage's Pond the bees have chosen to nest in a path
through a meadow located approximately 200 feet from the rose-mallow
plants, and 500 feet from the pond. There
are
probably a couple hundred burrows total, aggregated in a few
spots along a roughly 100-foot stretch of the path.
Aerial view of Ptilothrix nest site, the
rose-mallow marsh, and the open water of Stage's Pond.
Ptilothrix nesting area along path through
meadow, Stage's Pond, Pickaway County, August 13, 2008.
Ptilothrix nest area. August 20, 2008, Stage's Pond, Pickaway County,
Ohio.
In a detailed study of this bee, R.W. Rust (1980) explained
that
the female constructs tubular soil burrows terminated by urn-shaped
cells lined with a soil-wax mixture. Each cell is provisioned with a
chickpea-sized ball of pollen grains pasted together with nectar, and a
solitary egg. They're shown about life-size in
the left-hand portion of the figure below.
Ptilthrix burrow as depicted in Rust, R.W.
1980. The Biology of Ptilothrix bombiformis
(Hymenoptera: Anthophoridae). Journal of the Kansas Entomological
Society 53:427-436.
Nest construction begins with the bee moistening the hard-packed
surface soil with water she slurped up from the pond. First
with
her mandibles and then, as the hole gets deeper, with her abdomen, she
pushes the soil up and out of the hole. She pirouettes upside-down while she does this.
Ptilothrix initiating nest-burrow
construction, August 13, 2008, Stages Pond, Pickaway County, Ohio.
Here's a blurry little
YouTube video showing this early stage of nest burrow construction.
Later in construction of the nest burrow, when it is so deep that the
soil
cannot simply be pushed away, the bee molds the soil into little
dirt-bomb pellets
that are tossed away by her hind legs.
Ptilothrix in late stages of nest burrow
excavatation. She is doing a head-stand in the tunnel. The motion of her
hind legs is evident at 1/500 second exposure. The soil pellet, flying
away and to the left, is in mid-air.
Here's a looping animation (it goes on forever) of 14 still images taken moments apart, showing a female excavating a nest burrow.
Here's a YouTube video of the soil-tossing.
When the nest burrow is
complete, it is time to provision the cell (or cells) within with a
pollen/nectar ball as shown in the Rust (1980) illustration above. This
takes place in the
morning, when the bees, looking like little yellow pom-poms, can be
seen
arriving with full loads of pollen and, a couple of minutes later,
departing to get more. (The afternoon is apparently spent making
additional nest burrows.)
Ptilothrix enters nest with pollen. August 13,
2008, Stage's Pond, Pickaway County, Ohio.
Here's a foggy
little YouTube video showing Ptilothrix bringing pollen to the nest
site.
Nesting bees are
apparently cautious about
exiting the nest burrow. They linger at its mouth for some time, and
quickly duck back down when something large
nearby, holding a camera, moves conspicuously.
Ptilothrix at the mouth of her burrow, about to embark
on another pollen-gathering
mission. Note the yellow pollen grains littering the
entrance. August 19, 2008, Stage's Pond, Pickaway County, Ohio.
After completion --when
each cell contains
an egg and its pollen/nectar provision -- the burrow is filled with
loosely packed soil. The species overwinters as larvae. Adults emerge in
the spring.
Nest burrows of Ptilothrix loosely filled with soil.
August 19, 2008, Stage's Pond, Pickaway County, Ohio.
