Ramble Report August 6 2015

Today's report was written by Dale Hoyt. The photos that appear in this blog are taken by Don Hunter; you can see all the photos Don took of today'sRamble here.

23 Ramblers were with us today.

Today's Reading: Bob Ambrose, our resident poet, recited a new poem that was inspired by our Nature Rambles. You can findit here on Bob's private site.

(If you don't have permission drop Bob an email and ask him for permission to visit his site.)

Today's route: Leaving the arbor, we made our way down the paved path to the Flower Bridge and made our way through the Asian section, veering left at the big rock and going through the Native American section and Herb and Physic section on our way to the Heritage Garden.  Leaving the Heritage Garden, we made our way into the Flower Garden, past the meadows and entered the forest via the Purple Trail spur.  After connecting with the Purple Trail proper, we made our way back to the International Garden and passed back through the Herb and Physic Garden on our way to the Conservatory, where we quickly found Donderos.

At the arbor: before we started I passed around a specimen of an unusual insect that I found at the garden Wednesday – a pelecinid wasp. It has an abdomen about three inches long and parasitizes beetle grubs that live soil as well as wood-boring beetles that live in rotten wood. How the wasp locates the grubs is a mystery, but she must probe down into the earth with her long abdomen to lay her egg on the victim.

Catherine brought a live cicada and I got it to make some noise – not exactly like it would in a normal chorus but enough to be amazed by. Later on I spent some time talking about how the sound is produced.

Imperial moth on restroom siding

At the door of the women's restroom: resting on the wood siding was a beautiful Imperial moth. During the day moths often rest in situations that match their coloration. This was not a perfect match to the background, but maybe we can get the garden to paint the restrooms a mustard color.

Male Tiger swallowtail (note absence of blue on hind wing margin)

On the way to the bridge: at the flower bed next to the path we stopped to puzzle over some plants that none of us has been able to identify, even those that know the local flora. We still can't identify them.

Brown marmorated stink bug

At the international bridge: Rosemary spotted a Tiger swallowtail, the state butterfly. I netted it and quizzed everyone who was on the ramble two weeks ago – What sex is it and why? The ramblers got an "A." It was a male tiger swallowtail because it lacked the blue coloration on the dark border of the hind wing upper surface. At this spot George noticed a small, brown bug – a Brown marmorated stink bug (BMSB), a recent invader of our state. Some stink bugs are predators, but others suck the juices out of plants. The BMSB threatens to become a significant pest of soybeans in Georgia and is a nuisance in homes when it gathers in large numbers to pass the winter in attics or crawl spaces.

Bottlebrush buckeye fruit

Past the bridge: we noticed that the bottlebrush buckeye bears a few developing fruits. Out of the thousands of flowers that were present earlier in the season only a very small percentage were "perfect." A perfect flower has both stamens and pistil, the male and female structures of the flower. All the other flowers were staminate (males), producing pollen only – they could never produce any fruit. You can get an idea of how uncommon those perfect flowers are if you find a flower stalk with some developing fruit and count the scars where the staminate flowers once were.

Along the way to the Hop arbor someone spotted the web of a Bowl-and-Doily spider in the bushes to the left of the path. At the Physic garden  we saw a large, black solitary wasp nectaring on one of the mints. Our general consensus was that it might be a spider hunter.

Hops

At the Hop arbor: Many people have heard of hops and know it has something to do with beer. The vines growing on this arbor are hop vines and they have developing fruits that look like small, leafy globes. These are the hops. They are added to beer to give it that bitter bite. And they are the source for the name of one of our common trees, the Hop hornbeam. It is so-called because its fruits resemble those of the hop vine. The next time you walk on the White trail to the power line right of way notice the hop hornbeams to the right of the path. This year they are loaded with their hop-like fruit.

The Pawpaw patch: Our newest rambler, Jeff, told us about the development of one of the first cultivars of pawpaw. A man named Corwin Davis in 1959 found a pawpaw with delicious fruit growing in the wild near Bellevue, Michigan. From that tree he established a variety named "Davis" and introduced it to the trade in 1961. Jeff noted that there are problems getting pawpaw to set fruit for two reasons: a shortage of pollinators or absence of a different variety of pawpaw. The first problem, absence of pollinators, can be solved by hand pollination or encouraging the natural pollinators to find your pawpaws. Davis (and Jeff) do this by hanging buckets of rotting meat in their pawpaw patch to attract flies, the natural pollinators. The second problem is that  pawpaws are self incompatible. This means that pollen from flowers on the same tree will not be effective in producing fruit. This includes the root suckers that pawpaws send up, which are literally the same tree – the same as if you took cuttings from the tree. Pollen from these root suckers cannot successfully pollinate their parent tree.

The sorghum ecosystem: We arrived at the sorghum patch and discovered that the insect activity this morning was many times greater than it was two weeks ago, when we last visited. There is a reason for this increased activity and it starts with the sorghum. Sorghum is can be grown for grain, forage or silage but in the southeast, especially, it was also used as a source of sweet syrup. It is delicious when poured over hot biscuits or pancakes for breakfast. The sorghum varieties grown for syrup production were selectively bred to produce a lot of sugar. All that sugar circulating through the sorghum sap attracts sap-feeding insects and they, in turn, attract things that want to eat them. Plus, as you'll see, there is a by-product of the sorghum-sap feeder interaction that attracts another group of insects: nectar feeders.

The aphid: It's here that we encounter the first step in the food web: the aphid. Aphids are plant feeding insects that have piercing-sucking mouthparts. They stab their host plant with their pointy mouthparts and suck up the sap flowing within the plant. Sap is a dilute sugar solution, rich in carbohydrates, but poor in other nutrients. So to get a sufficient amount of the less common nutrients an aphid has to suck a lot of sap. That gives it more sugar than it needs, so the excess sugar passes right through and is pooped out. Most people know this as the "honeydew" that appears on the windshields of cars parked under aphid-infested trees. It's really aphid excrement. And it's sticky with sugar.

Aphids on Sorghum leaf

Aphid reproduction: Once an aphid has found its host plant and started feeding it begins to reproduce. It doesn't need to mate and it doesn't even need to lay eggs – it gives birth to living young, genetically identical to their mother, so, in a sense she is giving birth to her own twins. Not only that, the newly born aphids have similar young already developing in their reproductive tracts, just waiting to be born. The new born aphids mature in about three days, depending on temperature. Each aphid produces anywhere from 30 to 60 young, so you can see that the aphid population can explode very rapidly. A glance at the underside of the sorghum leaves confirms this; they are literally covered with aphids.

There is more to the aphid life history, though. How do they get to their food plants? Sometime during their life aphids can produce winged forms. These are the disperser generation – they can fly from their current home and find uncolonized plants. In some of the accompanying photos you can find a few winged aphids.

Note: in the photo above the white things are the molted skins of aphid nymphs; the larger orange things are aphids and the elongate gray things are winged aphids.

Where there are a lot of aphids under the leaves there will be a lot of honeydew on the upper surface of the leaves below. (Excrement falls.) This combination, aphids plus honeydew, attracts two types of insects: those that eat aphids and those that like sugar.

The sugar-eaters: These are mostly found on the upper surface of the sorghum leaves, where the honeydew is found. They are mostly insects that would be found nectaring on flowers if concentrated honeydew weren't available: wasps, flies, butterflies and the occasional bee. The number of different kinds we found was impressive.

Ladybug eggs (the cluster of light orange objects) among the aphids

Ladybug larvae of various sizes

Mealybug Destroyer (top center); ladybug larvae among the aphids

 

Adult ladybug; Mealybug Destroyer (left)

The aphid predators: One of the insects that loves to eat aphids is the ladybug. There are many different species of ladybugs, but we only observed two kinds: 1) the Asian multicolored lady beetle (Harmonia axyridis), and 2) the Mealybug Destroyer (Cryptolaemus montrouzieri). We found all stages in the life cycle of the first (egg, larva, pupa, adult) and only the larval stage of second.

More about the butterflies: Most of us saw two kinds of butterflies, the red spotted purple and two species of hairstreaks.

Red spotted purple butterfly

Red spotted purple: It's not really purple and the spots are more orange than red, but that's the name it's been given. One interesting thing about its coloration the iridescent blue on the upper surface of the hind wings. The actual color of this part of the wing depends a lot on your angle of view. From some directions it looks more green and from others it looks more blue. This is because the color is not due to a pigment. It is a structural color, caused by how light is reflected and refracted from the surface of the scales on the wings. Often this is true of the color blue in nature; e.g., the sky is blue because of the scattering of other wavelengths of light as it passes through the atmosphere. But back to the butterfly. The red spotted purple seldom comes to flowers; it is mostly attracted to rotting fruit and dung. It is likely that was attracted to the sorghum because when the humidity is high the apid honeydew starts to ferment. Fermentation produces alcohol which can be found in decaying fruits. The sorghum plus aphid combination is like a neighborhood pub, a place where you can drop in for a little nip.

Great Purple Hairstreak

Oak Hairstreak

Hairstreak butterflies: We saw two kinds of hairstreaks: the great purple hairstreak and the oak hairstreak. Hairstreaks get their name from one or two fine, hair-like projections on their hind wings. At the base of these hairs there is usually a brightly colored spot. Together, the spot and the hair-like projection(s) resemble an eye and antenna. When a hairstreak has landed this resemblance is enhanced by the way it holds and moves the wings. The wings are held together over the back and the two hind wings are rubbed together in an up-and-down motion. Hold your hands at arm's length in front of your body, thumbs up and palms facing each other. Now bring them together so your palms and fingers meet. Now rotate your hands, keeping them in contact with each other. This is the motion that the hairstreak performs with its hind wings. Don captured this motion in a movieof the great purple hairstreak. Rosemary also filmed the same sequence toward the end of her video of our ramble. 

In both videos you can see that movement would attract the attention of a predator toward the hind wings and away from the real head of the butterfly.

Bald face hornet (social wasp)

Cicada killer (solitary wasp)

 

Another solitary wasp

The solitary and social wasps: Most of the Hymenoptera we found on the sorghum were what are called solitary wasps. These do not live in colonies and are not divided into castes, like the workers and queens of ants and honeybees. They individually build a nest that they alone provision with food for their offspring. The nest may be a hole in the ground or it may be constructed from mud. Some of you may have seen mud dauber nests under your deck, if you have one. These solitary wasps hunt for living prey that they paralyze by stinging. It motionless but still living insect is then carried back to the next and an egg laid on it. When the egg hatches the larva begins to consume the living meal provided by its mother. Each kind of solitary wasp specializes on a different type of prey: caterpillars, crickets, grasshoppers, spiders. One of the largest wasps in the southeast specializes on cicadas. It is called – guess what – a cicada killer.

After the sorghum: on our way to the Purple trail we passed a plant, not in flower, that reminded Jeff of an Amaryllis. He told us that he had seen a type of Amaryllis flowering in a very arid region of Africa at a time when you would think that a plant with succulent green leaves would be devoured by herbivores. Yet, it stood there, untouched. Why? Because every part of the Amaryllis is deadly toxic. Something to remember if you have young children or cats that might eat leaves.

Cicada (possibly Scissors grinder cicada)

Cicada: I carried Catherine's cicada with me and waited until we reached the shade of the Purple trail before stopping to demonstrate its noise making. If you gently hold a cicada by its thorax it will attempt to escape by flying and make a loud squawking sound at the same time. But the sound is not made by the wings. Cicadas have special sound producing organs called tymbals, located on each side of the body on the first segment of the abdomen. Each tymbal is made of a stiff membrane to which a muscle is attached. When the muscle contracts the membrane bends with a "pop." When the muscle relaxes the membrane returns to its resting position. The droning call of the cicada is produced by the rapidly repeated contraction of the tympal muscles. The sound is amplified by a hollow resonating chamber the surrounds each tymbal. Most people are surprised when they hear how loud a noise such a small insect can make.

Finally in the shade we cooled off as we made our way back to the Conservatory and Donderos'.

Velvet ant AKA Cow killer
(not really an ant -- it's a wingless wasp)

Velvet ant: While sipping our drinks some of the Garden staff called us outside to see beautiful insect dressed out in University of Georgia colors: a velvet ant. Velvet ants aren't really ants. They are wingless wasps. They have a very potent sting, so don't try to pick one up with your bare hands. (Another common name for them is "cow killer." Their sting is not quite that strong, but it is very painful – I speak from personal experience. Velvet ants are parasites of other solitary bees and wasps. Only the females are wingless; the males look very different and have wings.

Maybe the velvet ant could be Georgia's mascot?

SUMMARY OF OBSERVED SPECIES:

Cicada	Neotibicen sp. probably N. pruinosa
Pelecinid wasp	Pelecinus polyturator
Imperial Moth	Eacles imperialis
Eastern tiger swallowtail	Papilio glaucus
Brown marmorated stink bug	Halyomorpha halys
Bottlebrush buckeyes	Aesculus parviflorum
Daddy longlegs	Order Opiliones
Bowl and doily spider	Frontinella communis
Solitary spider wasp	Family Pompilidae
Unidentified pycnanthemum	Pycnanthemum sp.
Common evening primrose	Oenothera biennis
Common Hops	Humulus lupulus
Paw paw	Asimina triloba
Sorghum	Sorghum sp.
White sugarcane aphids	Melanaphis sacchari
Nine spotted ladybug	Harmonia axyridis
Oak hairstreak	Satyrium favonius
Great purple hairstreak	Atlides halesus
Cicada killer	Sphecius speciosus
Ailanthus webworm moth	Atteva aurea
Leaf footed bug	Family Coreidae
Red spotted purple butterfly	Limenitis arthemis
Chalcid wasp	Family Chalcididae
Potter wasp	Family Vespidae
Black horse fly	Family Tabanidae
Summer azure butterfly	Celastrina neglecta
Spotted beebalm	Monarda punctata
Velvet ant/Cow killer	Dasymutilla occidentalis