June’s Featured Species: Desert Shadowdamsel (Palaemnema domina)
S17177 Desert Shadowdamsel, Palaemnema domina, male. Bonita Creek, Graham Co., Arizona; 1 August 2007; Dennis Paulson photo.
This month’s DSA species’ focus is the Desert Shadowdamsel (Palaemnema domina). It is in the Platystictidae, the shadowdamsel family. This moderate-sized slender damselfly is 35-44 cm (1.3-1.7 inches) long and is found at small, clear rocky streams bordered by dense vegetation. It is found in southeastern Arizona, south through Mexico to Nicaragua. Follow Dennis Paulson as he reflects on his experiences with this elusive species and other members of its genus.
Thriving in the Shadows
One of my favorite groups of odonates is the genus Palaemnema, 43 species of shadowdamsels in the family Platystictidae. The family is more diverse in the Old World, with 238 species in nine genera in southern Asia. All seem to be shade-lovers, the source of the common name for Palaemnema.
But we can thank the Belgian odonatologist Baron Edmond de Sélys-Longchamps for in 1860 coining the delightful generic name Palaemnema, which means “old memories.”
Perhaps because Philip Calvert, the first monographer of the genus, lived for a year in Costa Rica, it is well known there, with 11 described species, four of them endemic, and several still undescribed!
C43833 Nathalia Shadowdamsel, Palaemnema nathalia, male. Rio Corobici, Guanacaste Prov., Costa Rica; 7 July 2017; Dennis Paulson photo.
Mexico is home to eight species, four of them found nowhere else. Thirteen species are known from Colombia, and the genus occurs south to Peru and east to Venezuela, with one species extending farther east into the Guianas and northern Brazil.
E68255 Ink-tipped Shadowdamsel, Palaemnema paulirica, male. San Miguel de Matina, Limón Prov., Costa Rica; 18 October 2023; Smith photo.
One of these basically tropical damselflies has even crossed the border and is known from a few streams in southeastern Arizona. That is Palaemnema domina, the Desert Shadowdamsel. My wife, Netta Smith, and I found this species in numbers at Bonita Creek in Graham County, but they didn't come easy. They perch and forage among dense tangles, such as the root masses of fallen cottonwoods, and we had to look carefully and thoroughly in such places.
DiP00727 Bonita Creek, Graham Co., AZ; 28 May 2019. Dennis Paulson photo.
Shadowdamsels really deserve their name, standing out in the order by not needing sunlight to carry on their activities. Of course, they aren't the only tropical odonates like that, but they are the only ones I have looked for while crawling through the underbrush on hands and knees near a promising stream. When collecting Palaemnema, you may have better luck snatching one off a leaf with your fingers than swinging a net through the foliage.
C17007 Desert Shadowdamsel, Palaemnema domina, female. Lower Eagle Creek, Greenlee Co., Arizona; 28 August 2015; Netta Smith photo.
Shadowdamsels are so elusive that we don't know much about their lives. They are all stream-dwellers, and they have very distinctive nymphs, somewhat termite-shaped. I don't think anyone has kept them in captivity, and I don't think we know what they eat, presumably small invertebrates. They have been found living among rocks and gravel.
(DP)1 Shadowdamsel, Palaemnema sp., nymph. Rincón de Osa, Puntarenas Prov., Costa Rica; 8 March 1967; Dennis Paulson photo.
We also know little about what the adults eat. With long leg spines and wings held above the abdomen, they may be salliers, flying out to capture small flying insects just as a dancer (Argia) or a flycatcher would. I have never seen one feeding.
Their reproductive behavior has some fascinating turns. Males come to the water much earlier than other damselflies, again apparently not needing the sun. Males on territory often open and close their wings, surely a sign to repel other males from their immediate vicinity. Fancifully, I wonder if it also attracts females.
(DP)4 Shadowdamsel, Palaemnema sp. (undescribed), male opening wings. Rincón de Osa, Puntarenas Prov., Costa Rica; 18 March 1967; Dennis Paulson photo.
Males have been seen in numbers together at a stream, in a situation much like the leks of some birds. Females would approach and be clasped by a male, then the two flying away to land in a tree for a very brief copulation.
(DP)4 Desert Shadowdamsel, Palaemnema domina, pair in tandem. La Palma, Nayarit, Mexico; 15 September 2001. Dennis Paulson photo.
After mating much like other damselflies, the female oviposits over or near the water, different species in different plants, both woody and herbaceous. The pair does not remain in tandem, but the male perches very close to the female as she lays her eggs, guarding her against other males. I have not seen this behavior in any other damselflies, and I wish I had had a grant to study platystictids all over the world.
(DP)6 Shadowdamsel, Palaemnema sp. (undescribed), male guarding ovipositing female. 10 mi N Varablanca, Alajuela Prov., Costa Rica; 24 June 1967; Dennis Paulson photo.
Next time you're near a tropical stream, check out the shadows. We have much to learn about these damsels!
Dennis Paulson is a biologist and a naturalist who grew up in Miami, exposed to subtropical nature in all its glory while southern Florida was still largely unspoiled. He received his Ph.D. in Zoology from the University of Miami in 1966 with a study of the dragonflies of southern Florida, and shortly thereafter he moved to Seattle, where he has lived ever since. He recently retired after 15 years of being the Director of the Slater Museum of Natural History at the University of Puget Sound, where he also taught in the Biology Department. He has also led nature tours and traveled to all continents.
Paulson has published over 75 scientific papers on his favorite animals, and his contributions to natural history include these books: Shorebirds of the Pacific Northwest; Shorebirds of North America: The Photographic Guide; Exotic Birds; Alaska: The Ecotraveller’s Wildlife Guide; Dragonflies and Damselflies of the West;, Dragonflies and Damselflies of the East; Dragonflies and Damselflies: A Natural History; ABA Field Guide to the Birds of Washington; and Dragonflies and Damselflies of Costa Rica.
