Himalayan blackberry — the flowers are kind of pretty and the fruit can be tasty, but the thorny branches multiply every year into a snaggle of dead (and prickly!) canes. A closer examination, however, shows there is life in some of those old canes.
In late spring and early summer, look for canes where the inside has been hollowed out. The woodworkers responsible for this precise drilling are small carpenter bees, genus Ceratina.
Just like people, small carpenter bees can be a little complicated. Some live a solitary life (each female builds and maintains her own nest), and some live socially (a reproductive female gets help from others to build and maintain a nest).
When building their nests, Ceratina females bore holes up to 30 cm (12 inches) deep into pithy plant stems to create a secure cell into which she places pollen and provisions and one single egg. After closing the cell with chewed-up plant matter, she then repeats the process, working her way back to the stem entrance.
The eggs hatch and the larvae feed on the pollen, eventually maturing and pupating. Emergence is in the same year. Atypical of most solitary bees, Ceratina mothers remain in or near the nest and defend their offspring until they mature.
The new adults overwinter in the hollow stems, ready to start the process anew the following spring. Unlike most native bees, the original female can also overwinter and raise another brood in the next year. Isn’t that a fascinating blackberry crop?