Katie's Sightings

Neighborhood News!

Douglas Squirrel/Chickaree — Tamiasciurus douglasii

Last week I spotted a Chickaree with something in its mouth on a nearby tree. To my delight it stopped and ate its "lunch" while keeping an eye on me! I was surprised to see that it was eating the larvae in a Ruptured Twig Gall. I have seen woodpeckers feeding on these galls, but never a squirrel! I made a short movie of it chewing on the gall, which you can see just below the gall photo.

Ruptured Twig Gall (made by a tiny wasp — Callirhytus perdens)

These galls are made by tiny wasps that lay their eggs on the twigs of deciduous trees, mainly Black Oak and Live Oak in our area. As the larvae develop under the bark, the twig ruptures and eventually expels the larval capsules onto the ground. The linear fissures remaining on the stem become black.

Downy Woodpecker feeding on a Ruptured Twig Gall
Dryobates pubescens — Callirhytus perdensWoodpeckers will also eat the grubs found in galls. I watched this Downy Woodpecker feed exclusively on these ruptured twig galls for several minutes! Galls containing larvae are an important food source during the winter, when insects and their larvae are scarce.

In the winter, I have often seen Downy Woodpeckers also feeding on the larvae in Mossy Rose Galls. The larvae inside these galls are pretty big, about half an inch long! The following information about these galls is from bygl.osu.edu.

“The hairy-looking galls are produced under the direction of the gall-wasp, Diplolepis rosae (family Cynipidae). Ridding roses of the galls rids them of the wasp.

“The wasp occurs both in Europe and North America and will produce their characteristic galls on several species in the Rosa genus. They are most commonly found in Ohio on hybrid tea roses; however, I've also seen them on multiflora rose. Old galls look like a ball of moss stuck on the rose stems, thus the common name.

“Cutting the current galls open will reveal individual chambers, each housing a single wasp larva. The overall size of the gall depends on the number of larval chambers. Single-chambered galls usually measure less than 1" in diameter. Multi-chambered galls may measure over 2" in diameter, filaments included.

“The wasps have one generation per year. Females initiate gall formation when they use their ovipositors (= stingers) to insert eggs into leaf buds in the spring. The resulting wasp larvae exude chemicals that further direct gall formation.

“The galls change color from light green to crimson red as the wasp larvae mature. Late instar larvae spend the winter in dark reddish-brown galls and new adults emerge in the spring. Spent galls become grayish-brown and often remain attached throughout the season.

“As with most plant galls, mossy rose galls cause no harm to the overall health of their rose hosts. In fact, I believe they add ornamental value to roses, but I may be gall-biased: love thou the rose gall.”

Your questions and comments are appreciated. Please feel free to email me at northyubanaturalist@gmail.com. Thanks!