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| Great Golden Digger Wasp (Sphex ichneumoneus) on native buckwheat |
Gardeners are learning to appreciate
the diversity of native
pollinators, in part due to the activities of National Pollinator Week (the 3rd
week in June). To learn more about
pollinators in general, see our June 2013 posting (http://mother-natures-backyard.blogspot.com/2013/06/life-friendly-gardening-planning-for.html).
Among
the warm weather pollinators are the wasps.
While many gardeners associate wasps with nasty stings, many are mild
mannered and rarely sting humans. Most
are true garden heroes, functioning not only as pollinators but as predators of
unwanted garden creatures. They should be welcomed, not feared, by local gardeners.
The
insect Family Sphecidae – the Thread-waisted
Wasps – includes digger wasps, mud daubers, sand wasps and sphecid wasps. These insects have distinctive long, stalked abdomens,
giving the body a ‘thread-waisted’ or ‘wasp-waisted’ appearance. We plan to write several blog posts about
this interesting – and locally common – group of insects.
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| Female Burrowing Wasp (Sphex lucae) |
Most Thread-waisted wasps nest in the ground,
usually in areas that have sparse or no vegetation. Most are solitary nesters. Adults feed on
floral nectar, honeydew, and body fluids of their prey. Their larvae feed on
the paralyzed bodies of a variety of arthropods including spiders,
grasshoppers, and caterpillars. Adults provision the nests prior to laying
eggs.
The taxonomy of the Family Sphecidae has been recently revised [1]. It currently contains about 130 genera and
over 700 species worldwide. The Family is divided into Sub-families and
Tribes, based on similarities in morphology (appearance) and DNA [1]. The Tribe Sphecini
(in the Sub-family Sphecinae)
includes two genera (Isodontia; Sphex). The Sphecini are large, strong flyers, active during the warm/hot part
of the year. Several species of Isodontia and Sphex are known to visit S. California gardens, particularly those with
native plants. So, you likely have seen them in local gardens.
Two Sphex
species are well-documented from S. California. Both Sphex ichneumoneus (Great Golden Digger Wasp; Great
Golden Sand Wasp) and Sphex lucae (Burrowing
Wasp) are seen routinely in Mother Nature’s Backyard (Gardena Willows Wetland
Preserve, Gardena, CA). We’ve had great
fun photographing these large insects; they are pretty and interesting to
watch. Here are some interesting facts about these
two wasps.
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| Great Golden Digger Wasp (Sphex ichneumoneus) |
Sphex
ichneumoneus - Great Golden Digger Wasp/Great
Golden Sand Wasp
Native
to the Western Hemisphere (from southern Canada to Central/South America and
the Caribbeans), the Great Golden Digger Wasp is impressive, indeed [2]. Usually between one-half inch and one inch
(1.25 to 2.5 cm.) in length (sometimes even larger), they are distinguished by
the golden pubescence (hairs) on their black head and thorax, their reddish
orange legs, and partly reddish orange bodies. Half of the back segment of their abdomen is
also black; the front segment and legs are a conspicuous reddish-orange. The scientific name is pronounced ‘SFEX ick-new-MOW-nee-us’.
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| Great Golden Digger Wasp (Sphex ichneumoneus) on Red buckwheat |
Great
Goldens are not uncommon in parks, gardens, wild lands and vacant lots; in
short, where ever there are flowering plants, grasshoppers/katydids and bare,
sandy ground for nest sites. They can be
seen in warm weather, usually from May to September in S. California. We’ve seen them primarily in June and July in
our area – they are particularly busy in the dry, sunny days of early summer.
While
large, these wasps are not aggressive unless handled, swatted, or otherwise
threatened. Approach them slowly and
respectfully; watch and photograph, but don’t touch. They are wary creatures, but tend to go about
their business if left alone. They are very active; you’ll probably have to
photograph them with a telephoto lens.
For more tips on photographing garden insects see: http://mother-natures-backyard.blogspot.com/2015/07/life-friendly-gardening-photographing.html
Great
Goldens are so large and colorful that they are easy to spot. They twitch their
wings, making them appear to flash rapidly - a behavior that attracts your
attention. The adults feed on flower
nectar and sap. They utilize a wide
variety of flowers. We see them mostly on
plants with many small flowers, particularly the summer-flowering native
buckwheats, yarrow and milkweeds.
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| Great Golden Digger Wasp (Sphex ichneumoneus) on Red buckwheat |
Great
Goldens (and other Sphex) are
solitary insects: they do not share the responsibilities of provisioning for
and raising their young. However, dozens or even hundreds of females have been seen
nesting in the same area. Some favored
sites are used year after year [2]. Adult
females hunt/collect crickets, grasshoppers and katydids to serve as food for
their larvae. Sphex ichneumoneus wasps track their prey, hence the name ‘ichneumoneus’,
Greek for tracker.
The
nesting behavior of Sphex ichneumoneus is well documented, in
large part due to the careful studies of several entomologists. For a detailed description see reference 3,
below. In late spring or summer, each
female constructs from 1 to 10 nests.
The nests are dug in bare sandy soil; in local gardens they are often in
pathways or other areas covered by decomposed granite (DG).
The
main tunnel is one-half inch (1.25 cm) in diameter and four to six inches
(10-15 cm) deep. From one to seven brood
cells radiate off the end of the main tunnel.
These are where eggs are laid and larval provisions are stored. The entrance to the nest is covered up (to
hide it) each time the female leaves.
Great
Goldens hunt for crickets (Gryllidae), grasshoppers (Trimerotropis) and
katydids (Tettigoniidae) to serve as food for their young. The prey are paralyzed with toxins in her
sting. Smaller prey are then picked up
and flown to the nest. Larger prey are
dragged along the ground by their antennas, which the Great Golden grasps with
her mouth [3].
All
parts of the nesting behavior are ritualized; they are repeated again and again
with very little variation. Upon
reaching the nest with her prey, the Great Golden first inspects the burrow
before dragging the prey inside. The
prey – an average of four per brood cell – remain alive but paralyzed until
eaten by the larvae. One egg is
deposited per prey and the eggs hatch several days after being laid.
Great
Goldens have but a single generation per year.
The larvae spend the winter in the underground nests. They emerge as adults the following spring,
and the cycle goes on.
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| Great Golden Digger Wasp (Sphex ichneumoneus) on Red buckwheat |
For
more pictures of the Great Golden Digger Wasp see:
 |
| Female Burrowing Wasp (Sphex lucae) on 'Island Pink' yarrow |
Sphex lucae - Burrowing
Wasp
The
Burrowing Wasp, AKA the Orange Katydid Wasp, is another Sphex species we see this time of year. It is sometimes also known
as Fernaldina lucae. The
scientific name is pronounced ‘SFEX
LOO-cheh’ (or LEEOO-chuh). The
species was named by Henri Louis Frédéric de Saussure (1829-1905), a Swiss
mineralogist and entomologist, and a prolific taxonomist [4]. He was particularly interested in the
solitary wasps.
Sphex lucae is native to Western N. America from
southern British Columbia, Canada, to the U.S. Southwest (AZ, NM, UT, TX, ID,
CO, OK), California, Baja California and northern Mexico [5, 6]. As with Sphex
ichneumoneus, the Burrowing Wasp is
found where flowers, katydids and bare ground are available.
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| Burrowing Wasp (Sphex lucae) - female |
The
Burrowing Wasp exhibits sexual dimorphism; the male and female of the species
look different. The male is smaller (3/4 to 1 inch; 2.2-2.5 cm) in length,
slender and all black with violet reflections on the wings. The females are slightly larger (to 30 mm;
1.2 inches) and more robust than the males.
They are also more colorful: black with a red abdomen, and yellowish or
violaceous wings [6]. Unfortunately, we
have mostly photos of the females at present – we’ll try to remedy that soon. Note that face, legs and thorax are
completely black in this species.
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| Burrowing Wasp (Sphex lucae) - male |
The nesting behavior of Sphex
lucae is similar to
that of Sphex ichneumoneus. The prey are
primarily Katydids. Adults nectar on
small flowers – native buckwheats and yarrow in our garden, but also acacias,
Melilotus and likely other species.
Males
are known to spend the night in clusters or ‘sleeping groups’ [6, 7]. The location may change from night to night,
but groups tend to remain together, sleeping in sheltered places (in flowers; under
leaves; under rock ledges).
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| Burrowing Wasp (Sphex lucae) - female - on Dune Backwheat |
For
more pictures of Sphex lucae see:
http://www.boldsystems.org/index.php/Taxbrowser_Taxonpage?taxid=9201
In
summary, the Sphex wasps are interesting and colorful additions to the
garden. They are mild-mannered, and
their behavior is fascinating to watch.
So enjoy them in the wild and in your garden – and, please, don’t get out the can of
Raid and kill them. They are
garden heroes, important to the garden ecosystem and important parts of our
natural heritage.
Like this posting? See our other insect posts at: http://mother-natures-backyard.blogspot.com/2016/07/insect-postings-mother-natures-backyard.html
________________________
3.
http://aggie-horticulture.tamu.edu/galveston/beneficials/beneficial-54_great_golden_digger_wasp.htm
We encourage your comments below.
If you have questions about insects or other gardening
topics you can e-mail us at : mothernaturesbackyard10@gmail.com
