Specimen Spotlight - A surprise within a Stemmadenia litoralis
While digitizing the family Apocynaceae for the Plants on Edge/Endless Forms Project, I made a surprising discovery. Pressed and dried in the corolla of a Stemmadenia litoralis flower was a large bee, its proboscis (tongue) fully extended as it enjoyed what would sadly be its final meal.
Known as the Milky Way Tree, Stemmadenia litoralis (a synonym of Tabernaemontana litoralis) is often planted as an ornamental. This specimen, collected in the vicinity of Orizaba, Mexico, by Mateo Botteri (1808-1877) in the latter half of the 19th century, would have welcomed Botteri with the sweet, musky scent of its blooming flowers. As is often the case when I work with specimens from two centuries past, I began to speculate about the conditions under which the collection was made. Was Botteri surprised by the bee when he looked back upon his collections made that day? Did he deliberately collect the bee and flower together in an effort to preserve their mutualistic relationship? My curiosity peaked. Since I could not go back in time to ask Botteri these questions myself, I decided to delve deeper into the relationship between this mystery bee and the Milky Way Tree.
With only a superficial understanding of Hymenoptera, I relied on a bee-savvy friend to provide an identification. Based on its large size and geographic range, the specimen fit the description of a genus of neotropical orchid bee called Eulaema. Like their common name would suggest, orchid bees are a major pollinator of Central American orchids, attracted by the compounds that give them their fragrance. While not an orchid, Stemmadenia litoralis smells enticing enough to attract orchid bees. Male orchid bees have evolved oversized back legs containing pockets that they use to gather unique combinations of scent compounds to attract female bees. In a wonderful example of mutualism, the bee increases its likelihood of mating by interacting with fragrant flowers while the flowers benefit from being pollinated.
Inspired by this specimen, I decided to exercise my affinity for illustration and bring both organisms back to life. Using watercolor and ink, I created a rendition of what it might look like as a Eulaema orchid bee approaches a Stemmadenia litoralis flower, proboscis extended and hind legs ready to scoop up scent compounds. Perhaps this is what Mateo Botteri saw moments before he snipped the branch from the tree. Whatever the case, this specimen now resides in perpetuity in the Gray Herbarium (and its database; barcode 02009693) to be appreciated by researchers and curious individuals alike.
- Madeline Schill, Curatorial Assistant
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Stemmadenia litoralis HUH barcode 02009693 | Watercolor by Madeline Schill |
References:
https://www.fs.usda.gov/wildflowers/pollinators/pollinator-of-the-month/orchid_bees.shtml
https://www.bbg.org/article/orchids_and_their_pollinators
https://homepage.ruhr-uni-bochum.de/thomas.eltz/obfragra.html
http://www.marriedtoplants.com/flowering-plants/stemmadenia-littoralis-the-milky-way-tree/
https://plants.jstor.org/stable/10.5555/al.ap.person.bm000041671