Empis snoddyi
Steyskal, 1969
Empis snoddyi is a of dance fly in the Empididae, described by Steyskal in 1969. It is to the Appalachian Mountains of the eastern United States. The species is notable for its highly specialized mating ritual in which males produce large, empty silk balloons as for females—a derived trait that represents an evolutionary departure from the prey-based gifts typical of related species.
Pronunciation
How to pronounce Empis snoddyi: //ˈɛm.pɪs ˈsnɒd.i.aɪ//
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Identification
Distinguished from other Empis by geographic restriction to southern Appalachians and the male's unique empty silk balloon . The combination of yellow legs with dark femoral ring, nearly , and grey-frosted dark helps separate it from sympatric empidids. Males of the subgenus Enoplempis (to which E. snoddyi belongs) possess enlarged teeth on the hind leg 'knee' joint (-tibia junction), visible under magnification.
Habitat
Mountainous areas of the southern Appalachian region. Specific microhabitat preferences within these montane environments are not documented.
Distribution
to the United States, restricted to mountainous areas from southern Virginia through North Carolina to northern Georgia.
Behavior
Males perform a distinctive mating ritual involving the production of large empty silk sacks () composed of hundreds of air-filled silk bubbles. The prothoracic basitarsus produces silk that forms irregular polygons of varying sizes. Males present these balloons to females during courtship. Large males with intermediately sized sacks have been observed to achieve the highest mating rates, suggesting on both body size and gift dimensions. The balloon gift appears to function as a signal of male rather than nutritional provision.
Similar Taxa
- Other Empis (Enoplempis) speciesOver 50 in this subgenus share the enlarged hind leg teeth in males; distinguished by geographic range and type
- Other Empididae providing prey-based nuptial giftsE. snoddyi is unique in providing empty silk balloons rather than prey, wrapped prey, or prey-filled sacks typical of the
More Details
Evolutionary significance of nuptial gift
The empty silk balloon of E. snoddyi is hypothesized to represent a derived trait from the ancestral condition of providing nutritious prey gifts. This evolutionary transition may represent an escalation in where the gift's value shifted from nutritional to signal-based.
Silk production mechanism
The male prothoracic basitarsus is modified for silk production. Males can vary silk output, resulting in irregular patterns of polygon sizes within individual balloons.