We’re going into overtime on “Ammophila Month,” so we can conclude with what may be the most elegant and impressive of all the eastern species in this genus: A. nigricans. This species is easily as large as A. procera, but readily identified by the lack of silver stripes on the thorax, the overall deep blue-black body with red on the abdomen, and the black wings.
I was fortunate enough to encounter this particular specimen around 5:00 PM on July 5, 2009 in South Deerfield, Massachusetts. She was in the process of finding a place to settle in for the night and was quite tolerant of my photographic activities. This is often the best time to look for Ammophila wasps in general, because of this “sleeping” behavior.
The wasps will grip a grass stem or twig with their jaws, then prop their slender bodies at about a forty-five degree angle away from their perch. It doesn’t look very comfortable, but this stiff posture appears to suit the wasps just fine. You can sometimes find several species of Ammophila in the same general vicinity as they bed down at dusk. There are certainly often several individuals of the same species in close proximity, as in the image below of an unidentified species.
When they are awake, females of Ammophila nigricans are all business. Each wasp digs a vertical or angled burrow in clayey or sandy soil, terminating in a horizontal chamber at the bottom. Once the nest is excavated, it is off to find a large caterpillar. Known hosts include the larvae of underwing moths (Catocala spp.), the locust underwing (Euparthenos nubilis), and zale moths (genus Zale). Those are hefty caterpillars, but then they are destined to feed the larva of a very robust wasp. This YouTube video may or may not depict A. nigricans, but the searching behavior must be very similar at the least. The female wasp is not likely to locate a caterpillar based on movement or color, as the caterpillars are very cryptic and usually resting stock still, feeding at night to avoid predators like the wasp. So, she must find her prey by touch.
I hope you have enjoyed this introduction to this genus of wasps, and that you are excited to find specimens of your own once the warm weather returns to your location. Meanwhile, feel free to share your past observations here. Happy holidays to you!