If you have white oak trees, and there’s a good chance you do, you’ve probably seen this week’s crawly. Meet the speckled gall wasp (Cynips mirabilis).
Let’s get the “don’t panic” portion out of the way. While galls on plants and trees may look a little funky, it’s very rare for any species of gall to cause any actual damage to the plant or tree.
Hundreds of species of arthropods live in and depend on oak trees, it’s in the best interest of all of them to do nothing more than some cosmetic damage to their home. There are even multiple species of gall wasps that specifically live in oaks, but the oaks keep on growing.
That said, galls like those of the speckled gall wasp are absolutely fascinating! As you can see by the photo the speckled gall wasp gets their name from their gall, not their appearance. If their name came from their looks, they’d be the “shining golden wasp”.
The photo also gives you a good idea as to why you’ve likely overlooked these bity beauties. The pictured female is perched on the tip of a cotton swab getting a drink of sugar water. All one-quarter of an inch of her easily fits on the cotton swab with room to spare.
Many adult gall wasps will hibernate over winter, so you may see some on warmer autumn days. In spring they will lay eggs at the base of newly sprouting leaves and then “The Amazing Life of a Gall” begins.
When the wasp lays their egg on the sprouting leaf, they use specialized glands to inject growth-regulating chemicals into the leaf. These interact with specific chemicals in the oak leaf to produce abnormal growths or “galls”.
The egg of the gall wasp is unharmed and completely encased inside the gall. When the larva hatches, they feed on the gall tissue and grow. In addition to holding nutrition for the young wasp, the inside of the speckled gall is also filled with hair-like filaments which act like packing material to protect the young wasp.
Galls are the ultimate “tiny houses”. They’re waterproof, insulated, fully stocked with food and nearly impenetrable to would-be predators and parasites.
The galls fall along with the leaves in autumn and the adult wasps chew their way out and find shelter for the winter. If you find a gall with a tiny hole in it, you know it’s empty; the wasp having successfully emerged.
The adult gall wasps are beneficial pollinators of late fall and early spring flowers and a food source for birds and various arthropods.
Fun facts: The abandoned galls can be used in crafting, you can even craft little gall wasps from old galls. Oak gall ink – which was used to pen the Declaration of Independence – can be made from the abandoned galls of various species of gall wasps who live in oaks.