280 days of Urbpandemonium #186

[urbpan]

Frankly, I'd never heard of the hackberry tree Celtis occidentalis* before my first encounter with the hackberry nipple gall. I think we can agree that's one of the most wonderful word combinations I've placed here. The galls are made by aphid-like insects called psyllids, in the genus Pachypsylla, including notably Pachypsylla celtidismamma.** The galls also harbor some non-gallmaking psyllids who benefit from their relatives' alteration of the hackberry leaf.


*Western hackberry

**Hackberry breast thick flea