SVASTRA LONG-HORNED BEES
Svastra are hefty, shaggy bees, best known for their prowess as sunflower pollinators. Svastra usually emerge in late summer or fall, a fact that helps distinguish them from similar long-horned bees of the genus Melissodes, which tend to appear in spring and early summer. The existence of Svastra in a given area is often indicative of a high-quality grassland habitat interlaced with a healthy population of wildflowers.
Like most long-horned bees, Svastra nest in the ground. They are typically solitary, but sometimes build nests close to one another in large groups. Svastra females also are known to share nests with one another: each bee provisions her own egg chambers with food stores for her offspring, while jointly excavating tunnels and nest entrances with other Svastra.
In 1982, while on a research expedition 20 miles southeast of Tuscon, prominent entomologist Jerome Rozen lit on a nest of Svastra sabinensis, the bee shown at right and below. He later described the S. sabinensis nest as being occupied simultaneously by two female bees. The nest had “a branched, meandering burrow descending to approximately 80 cm, at which level numerous cells occurred. The cells were vertical, elongate and lined with a non-waxlike waterproof lining. Parts of the nest were plugged with sorted pebbles. A single specimen of the parasitic bee, Triepeolus penicilliferus, was collected while trying to enter the nest.” Rozen brought the two female Svastra and the parasitic Triepeolus back with him to the American Museum of Natural History in New York.
Svastra and pollinator plants
The best known member of the genus Svastra within the United States is Svastra obliqua, commonly called the sunflower bee. This species is found in Texas and throughout the United States. S. obliqua is an essential pollinator of sunflowers in many areas.
The frisky Svastra, Svastra petulca, is the most common member of its genus at the National Butterfly Center. The frisky Svastra shares with Svastra obliqua a preference for composite flowers in the aster family -- including, for example, cowpen daisy, gaillardia and sunflowers.
At the National Butterfly Center, Svastra petulca long-horned bees appear in April. Male bees mob common sunflowers in the NBC gardens, and they are the only large bees at NBC that feed on Mexican hat, a flower in the aster family whose odd shape -- a tall brown column skirted by short orange petals -- makes an awkward landing pad for most large bees.
Some members of the genus Svastra are generalist pollinators that visit a fairly broad range of wildflowers. Svastra sabinensis long-horned bees feed principally on composite flowers in the family Asteraceae, but they also have been documented foraging on mallows, milkweeds and poppies of the genus Kallstroemia. At the National Butterfly Center, Svastra sabinensis long-horned bees feed principally on skeleton-leaf goldeneye during the fall.
A few Svastra species are specialist pollinators of cactus and of evening primrose.
Svastra vs. Melissodes and other long-horned bee genera
Generally, Svastra are medium-sized to large bees with hairy thoraxes, faces and legs. The bees' abdomens are often banded by dark-and-pale hairs or, less commonly, covered with short tawny hairs. The female Svastra has a dark clypeus (the face part above the jaws), while the male has a yellow clypeus, clearly visible to the naked eye. The antennae of Svastra are relatively short for long-horned bees, ordinarily reaching no farther than the first segment of the bee’s abdomen.
According to Wilson & Carril, authors of The Bees in Your Backyard, the name “Svastra” is Sanskrit for “sister.” The genus was first documented by the famed Argentinean naturalist Eduardo Ladislao Holmberg, a prolific science writer, author of science fiction and director of the Buenos Aires Zoological Gardens.
In the late 1800’s and early 1900’s, Holmberg, at times forsaking his longstanding interest in spiders, undertook a series of bee-collecting expeditions into the mountains of Argentina and the wilds of neighboring South American nations. He found several varieties of long-horned bees and named the genus Svastra, remarking on its similarity to its sister genus Melissoptila, which he also named.
In the years following, Svastra bees were classified as a subgenera belonging to the long-horned bee genus Melissodes. Svastra are similar to Melissodes because, among other qualities, female bees of both genera have feathery scopal hairs, carry pollen on their hind legs, and possess similarly-colored clypeuses (with females having dark clypeuses and males yellow ones).
Now relocated in their own genus, Svastra are differentiated from bees of the genus Melissodes in part by size. Entomologist T.B. Mitchell, author of the voluminous Bees of the Eastern United States, described Svastra generally as large and robust, noting that some of them were nearly as large as queen bumble bees (measuring up to 20 mm). Mitchell also wrote that Svastra females could be best distinguished from other long-horned bee genera by a single trait, visible to the naked eye: Svastra females have a tuft of long hairs in the middle of the metanotum (located near the back of the thorax). This trait is shown in the photo strip at right.
Other, more minute traits, not visible to the naked eye, also separate Svastra from Melissodes. Entomologist Sam Droege notes that Svastra have clearly oval tegulae (the nodes where the wing meets the bee’s body). Svastra also have spatulate hairs on their first two abdominal segments (T1 and T2) – that is, hairs that look like “tiny, transparent table knives" located at the base of T2 and near the rim of T1, which grow alongside more abundant simple hairs.
A female Sabine Svastra (Svastra sabinensis)
genera sometimes confused with Svastra. Svastra sometimes have dark-and-pale stripes on their abdomens but tend to be larger than Melissodes bees and to fly later in the year.
Distinguishing Svastra from other long-horned bee genera
A male Svastra petulca long-horned bee: note the bee's yellow clypeus, which is typical of males of the genus Svastra.
TAXONOMY OF SVASTRA BEES
Species shown below:
Svastra petulca (Frisky Svastra)
Svastra sabinensis (Sabine's Svastra)
Svastra Long-horned Bee Species of the National Butterfly Center
Svastra (Epimelissodes) sabinensis
Size: 14 mm (female)
Food plants at NBC:
Plant Family: Asteraceae
Svastra (Epimelissodes) petulca
Size: 16 mm (female); 14 mm (male)
Food plants at NBC:
Plant Family: Asteraceae
of female bee:
of male bee:
A female Sabine's Svastra
Species Identification: Svastra sabinensis
Svastra sabinensis is a magnificent long-horned bee, large and leonine and covered with golden hair. The bee's appearance is somewhat unusual – many Svastra bees have abdomens with black-and-pale bands. The abdomens of Svastra sabinensis bees, however, are clothed with short, tawny hairs.
Within Texas, Svastra sabinensis is fairly easily differentiated from other Svastra. The most commonly-seen Texas Svastra species include Svastra obliqua, S. compta, S. machaerantherae, S. petulca and S. texana. The last four of these have black abdomens striped with pale-and-dark bands. Svastra obliqua is shown below.
Svastra sabinensis ranges west to California, north to Colorado and south into Mexico.
A female Svastra petulca
A female Svastra petulca from above
A male Svastra petulca