Oaks- Strong Supporters of Woodland Life

A barred owl rests in an oak

A thousand stories come together as you observe all of the life associated with oak trees

One of my favorite things to do is to take a lightweight three- legged folding stool out on hikes and sit down for a while in areas that show a promise of something good to come if I can simply wait a bit. It is always a surprise to discover all the activity going on that I would have missed because of a failure to employ the railroad method of outdoor walking: “ stop, look and listen “.

Doe sleeping under an oak in the winter

Oaks provide a great opportunity to observe all kinds of life, as they are a major food source for many caterpillars, cicadas, katydids and other species of insects.. Holes from feeding insects, leaf shelters containing caterpillars and leaf or twig galls are just a few things you may notice. But a closer look will prove that is just the tip of the iceberg.

Tiny creatures seen crawling along twigs and leaf undersides may be the nymphs of some sort of tree hopper insect. Caterpillars might dangle down on silken threads, spiders may have woven webs among the branches and mushrooms arise from duff underneath the trees. Oaks provide nesting sites for many birds and animals, and food in the form of leaves, twigs and acorns.

Spider silk dangling from an oak on an October morning

Early in the spring when oaks are just beginning to show swollen buds, catbirds normally are back. And as leaves begin to unfurl, look and listen for scarlet tanagers and Baltimore orioles in the top of the canopy of mature oaks. There must be caterpillars there because you will see them poking around and under the newly opened leaves. Male red- bellied woodpeckers advertise the fact that they have constructed a fine nesting cavity suitable for any females in the area. The males can be hard to spot because they sit inside their hole and poke only their head out and sing sporadically all day. Because of past storms, many oaks have dead vertical limbs that are just what red- bellies like for drumming and excavating.

Male red bellied woodpecker sings from inside his newly created nesting hole

Oaks have the distinction of being the host for many gall insects. While most are not a threat to the health of the tree, they can occur in large numbers. One of the most common galls familiar to many people are those formed by the oak apple gall wasp. These are large and are a smooth with a limey green color. Neatly tucked inside is the larva of the wasp, safe and sound from predators. A gall of the wool sower wasp is associated with white oaks and it looks somewhat like a toasted marshmallow.

Wool sower wasp gall on white oak

Oaks are also the host plant for over 500 species of moth caterpillars, which makes them the champ when it comes to supplying bird food in Connecticut. From spring until fall, check out oak leaves for any caterpillars that may be there. Late in the summer, walking sticks might also be found on oaks.

 

Afflicted dagger caterpillar on an oak

Yellow-based tussock moth caterpillar on white oak

Butterflies such as the spring-flying Juvenal’s duskywing, banded hairstreak, striped hairstreak and red-spotted purples also use oaks as host plants for their caterpillars. If these butterflies are seen, check out any nearby oaks for the caterpillars.

Juvenal’s duskywing butterfly uses oaks as a host plant for its caterpillars

Several weevils are associated with oaks, among them the acorn weevil. The female lays an egg inside an acorn by chewing out a hole with its mouth and inserting one egg inside the developing fruit. Look for acorns in the fall that have a small round hole. This is evidence that the larva that was feeding inside has exited by chewing its way out. Sometimes squirrels can be seen turning acorns around in their paws as they look for these holes, or feel the weight of the acorn. They will not waste valuable time opening an acorn that will not supply a sufficient supply of food.

Female acorn weevil on red oak

New York weevil on oak

A few years ago, there were lacewing eggs everywhere on the undersides of all kinds of oaks. The next year- hardly any on oak, but there were a lot on cherries. In late summer. Lacewing larvae move about on the top of oak leaves with old molted exoskeletons and other debris piled on their backs. They look like little mobile fuzz balls.

 

Lacewing eggs under an oak leaf

Deer and turkeys rely on acorns for food during the fall and winter. Sometimes you can see the places under oaks where deer have dug through the snow looking for acorns. Gray, red or flying squirrels will also eat acorns and may also nest in the trees as well. Once year a pair of young flying squirrels were out during the day because their nesting hole was damaged by a fallen branch.

Young flying squirrel

The next time you see an oak, imagine all that may be happening on, around and under that tree. Look a little closer and see what you can find. And enjoy its shade at the same time.

 

Pamm Cooper

You have to look close to see the gray tree frog on this tree trunk

 

Life on an Oak Tree

Do you ever think about all the life going on around you- on plants, in the water and soil or whatever? Sometimes we just need to take a little time to stop and smell the roses ( I used to smell them as I ran by ) or spend some time looking a little closer at the world around us. It can certainly be eye- opening.

One of my favorite things to do is to take a lightweight three- legged folding stool out on hikes and sit down for a while in areas that show a promise of something good to come if I can simply wait a bit. It is always a surprise to discover all the activity going on that I would have missed because of a failure to employ the railroad method of outdoor walking: ‘ stop, look and listen “..  So over the years I have learned to heed the words of Paul Simon- “ slow down, you move too fast… “

Today my co-worker and I stopped to admire an oak and it became apparent that there was a lot of activity on its lower branches. Holes from feeding insects, leaf shelters and galls were just a few things we noticed. But a closer look proved that we had just seen the tip of the iceberg. Tiny creatures were crawling along twigs and leaf undersides that turned out to be yellow nymphs of some sort of tree hopper insect. And dangling down from the tree on silken threads were several tiny instars of Ashen Pinion caterpillars and some other, as yet unidentified, caterpillars. There were also two tiny gypsy moth caterpillars just beginning to show the definitive dots that run along their back.

Early in the spring when oaks are just beginning to break bud, catbirds normally are back. And as leaves begin to unfurl, look and listen for Scarlet Tanagers and Baltimore Orioles in the top of the canopy of mature oaks. There must be caterpillars there because you will see them poking around and under the newly opened leaves. This year there were an abundant amount of  male Red- bellied Woodpeckers advertising the fact that they thought they had constructed a fine nesting cavity suitable for any females  in the area. The males can be hard to spot because they sit inside their hole and poke only their head out and sing sporadically all day. Because of past storms, many oaks have dead vertical limbs that are just what red- bellies like for drumming and excavating.

Oaks have the distinction of being the host for many gall insects. While most are not a threat to the health of the tree, they can occur in large numbers on certain trees in  some years. One of the most common galls familiar to many people are those formed by the oak apple gall wasp. These are large and are a smooth with a  limey green color. Neatly tucked inside is the larva of the wasp, safe and sound from predators and with a good supply of food supplied by the oak’s abnormal growth caused by the trees response to chemicals the female wasp injected with her egg. There are other galls also, including “ potato “ and “ bullet “galls on twigs stems and rosette galls on leaves.

 

Oaks are also the host plant for over 500 species of caterpillars, which makes them the champ when it comes to supplying bird food in Connecticut. Right now you may see Ashen Pinions ballooning down on silken threads. Or flip leaves and look for tiny Gypsy Moth Caterpillars- only about an inch long right now. Many caterpillars form leaf shelters, or tents, where they hide during the day. Go out at night with a flashlight and look for these guys. Right now there are many sallows and pinions, but later in the summer the daggers and prominents abound, and I find these caterpillars a more exciting find. They are bigger and more interesting in shape and color, as well as sometimes having warty protuberances sporting long hairs. Most of these can be found either along leaf edges of on leaf undersides. Look for feeding damage and check out nearby leaves.

A little insect that may be overlooked is the acorn weevil. This  insect lays its eggs inside acorns by chewing out a hole with its mouth and inserting one egg inside the developing fruit. Look for acorns in the fall that have a small round hole. This is evidence that the larva that was feeding inside has pupated and exited as an adult by chewing its way out. Sometimes squirrels can be seen turning acorns around in their paws as they look for these holes, or feel the weight of the acorn. They will not waste valuable time opening an acorn that will not supply a sufficient supply of food.

 

A few years ago, there were lacewing eggs everywhere on the undersides of all kinds of oaks. The next year- hardly any on oak, but there were a lot on cherries. Several years ago there was a hard frost when oaks were flowering and that fall there were few, if any, acorns. Squirrel and chipmunk population were noticeably down the next year, perhaps because of a lack of food for the winter. Deer and turkeys also rely on acorns for food during the fall and winter. Sometimes you can see the places under oaks where deer have pawed aside the snow looking for any acorns that may be left.

So next time you see an oak, imagine all that is going on in, around and on that tree. And maybe look a little closer to discover a little of what that tree has going on. And enjoy its shade!

Pamm Cooper

 

Holes in My Acorns: The Acorn Weevil

Have you ever found an acorn with one or more small, perfect holes and wondered what kind of insect left it there?

  Photo: J. Aspinwall

It’s probably from the emerging larvae of the acorn weevil, Curculio sp.   Acorn weevils attack both red and white oaks and are found throughout the range of these trees.  Like other weevils, the acorn weevil has a long snout, in this case very long!  The snout of the female is sometimes even longer than her body.  The bent antennae come off the sides of the snout.  Check out this photo of an adult:   Photo: J. Aspinwall

Weevils are beetles and members of the insect order Coleoptera.  The life cycle of the acorn weevil takes one to two years.  The brown, 3/8” adults emerge in the spring and the female begins laying eggs in acorns in midsummer while they are still maturing on the trees.  She makes one or more holes per acorn with the mouthparts at the end of the snout and deposits a single egg in each hole.   After the larvae hatch, they feed within the acorn and are capable of consuming the entire nutmeat.  The legless larvae grow to about ¼ to 3/8” long and are creamy white with brown heads.  After the acorn falls to the ground, the larvae emerge and burrow into the soil.  They remain there for one to two years before pupating and emerging as adults in the spring.

If you find an acorn with a hole in it, you can break it open to look for the larvae (if you catch it soon enough) or their tunnels inside:

 Photo by J. Aspinwall

Where there has been acorn weevil activity, it may be hard to find acorns without any holes.  This is because squirrels leave them behind, knowing that they are not going to provide a good meal.  Smart squirrels!

Acorn weevils don’t usually harm the rest of the tree in any way so control is not practical or necessary.

This short video shows the larva emerging from an acorn.  It’s pretty entertaining because the larva is much bigger around than its hole so it has to work pretty hard to get out.  Remember when Winnie the Pooh tried to get out of Rabbit’s house after eating too much honey?  That’s the idea.  And here’s a warning for the sentimentalists: the ending is sad.

By J. Allen