American entomologist William Harris Ashmead had an eye for detail and an infatuation with insects. He must have liked fruit, too.
Living in Florida, he founded a publishing house to print agricultural tomes with a focus on bugs. His passion for pests was palpable, and in 1880 he penned a book called Orange Insects: A Treatise on the Injurious and Beneficial Insects Found on Orange Trees in Florida. This was just the beginning of his love affair with insects.
In his career as an entomologist, Ashmead identified and named more than 3,000 insect species, specializing in ants, beetles, wasps and parasitic insects. Among these, one creature has the gall to stand above the rest.
The blueberry stem gall wasp is one of his naming legacies, and the scientific name that Ashmead bestowed upon this small wasp is of interest. “Hemidas nubilipennis” is what he called this insect, and its name doesn’t describe what you might think!
“Pennis” is not, as one might assume, an alternate spelling, but rather it is a Latin root that roughly translates into “feathers” and describes the elongated shape of this insect’s most obvious feature — an ovipositor, a female appendage used for reproduction. Another etymological reference (to this entomological question) translates it as a description of the non-gender-specific tail of this wasp. And how exactly does the female use its namesake appendage? This wasp has devised an ingenious method of reproduction. In the summer, the female wasp lays eggs in either the shoot, twigs or stems of the blueberry plant. She then goes to the very tip of that shoot and sabotages it, stabbing it repeatedly with her ovipositor. This repeated piercing damages the tissue in the area that was attacked, and will deter the growth of the fruit as those buds are damaged by the stabbing. At the same time, the damaged tissue allows the plant’s nutrients to be redirected to the tumor-like growth (or gall) to nourish the wasp’s growing larvae.
All of this action happens inside the gall and cannot be seen. In the winter, the wasp larva lies in wait for a warmer season, when it will emerge as an adult. As it happens, the preponderance of these adult wasps will be female.
Evidence of H. nubilipennis is easy to find. Look no further than the high and low bush blueberries that grow wild about the Island. There you will see a kidney-shaped swelling on the tips of the stems and branches of blueberry bushes. These started off as spongy, green swellings in the summer and then dried and turned brown in the fall. They now appear as hard and woody tumors or galls.
An interesting side note, for those who may feel that these wasps are taking unfair advantage of the blueberry plants, is that other species of insects are in turn taking advantage of them!
Inside those galls are about a dozen blueberry stem gall wasps, plus possibly more than half a dozen other parasitic insects that take advantage of the wasps’ multi-chambered home. The exit strategy for the wasps is to preempt the bud break and chew out of the gall. Holes in galls will then be visible where the wasps or other parasitic insects have emerged. With the right timing, the galls can be collected in the spring and the insects’ emergence observed over time.
So there is really more to the story than meets the eye! Beneath the bumpy outer shell of the gall on the blueberry stem, a gregarious group of insect species is growing, out of sight but not out of mind, providing more for the insect-loving heirs of W. H. Ashmead to appreciate. And more for fruit lovers to fear!
Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown.