Tuesday, September 22, 2015

Yellowjackets

A Yellowjacket worker searches the forest floor for a meal for her and her nest mates.

     Yellowjackets (Vespula spp.) are social wasps who can be beneficial most of the year. They however often come in conflict with people, specially in the Fall. Because of their striped appearance, they are often confused with bees, and most stings are actually due to Yellowjackets rather than bees. They are more slender however, with the thin wasp waist, and normally not very hairy as compared to bees such as honeybees.
     Yellowjackets as adults feed on sugars, nectar, rotting fruit, and occasionally scavenge. They can be minor pollinators of some flowers, but just are not built for it since they do not need to collect pollen to feed their young. Instead, they feed their young proteins in the form of insects and spiders that they sting and bring back to their nests. In this manner, they can be beneficial in controlling some insect populations, though they will just as likely sting and kill a beneficial insect as they would any pest species. If their prey is too large, the wasps will bring it back in pieces or ingest it to regurgitate back to the nest's young later. For a video showing one trying to capture a large food item, please check out this short clip from the Capital Naturalist YouTube Channel:

     https://www.youtube.com/watch?v=lmAquJ7OZME

     Yellowjackets are social insects, with a queen laying eggs and workers (her daughters) providing such labor as building and repairing the nest, foraging for food, and defense. Males (drones) are produced once a year in the Fall. After mating, the newly fertilized queens find a secluded spots underground or in old logs to overwinter. The males die soon after mating. The old queen and her workers all die also, at least in our part of the country.
     In the spring, the new queen awakens and goes out to search for a place to start her nest. She often picks an old rodent burrow or rotten log. While most nests are underground, they will occasionally find open spaces in walls or build an aerial nest (there's one species, Aerial Yellowjackets, that almost always do). The nest is constructed of wood fibers that are chewed into pulp and then made into paper building material. This she uses to make the nest and the cells she lays her eggs into.


What it would look like if you broke into a Yellowjacket nest.

         After the first generation, workers take over most duties, but the queen is the only one who lays eggs. By the end of summer, the large paper nest may be the size of a basket ball and have 3,000 or even more workers. Because these structures are hidden underground or in old wood, we rarely see them. For a look at an active nest, please check out this short video clip from the Capital Naturalist YouTube Channel:

     https://www.youtube.com/watch?v=yc4LQRf318M


The inside of a Yellowjacket nest revealing paper cells, larvae, and even some emerging new workers.

     On a steady stream of chewed up insects and spiders, the young quickly multiply. Because the nests are hard to see, people sometimes stumble upon them. Early in the season, there may not be many workers ready to defend the nest, but by Fall the numbers have swelled and the workers are more than willing to give up their lives in defense of their siblings and mother.
     Only females can sting, since the stinger is a modified ovipositor or egg laying apparatus. Males thus cannot sting. Females can do so repeatedly, injecting venom that can be painful and which they normally reserve for capturing prey. Predators include bears, skunks, and raccoons, though these often try and raid nests when it is cooler or stop their attacks early if the defense gets to be overwhelming. Since Yellowjackets do not produce honey, these predators are simply raiding to eat the larvae.
     When a worker stings, it tags whatever it has stung with a chemical marker that then targets the victim for any new wasp to sting. Once so marked, the female workers will attack their enemy relentlessly and will sometimes follow the perceived aggressor for quite a while before ceasing. This of course can lead to dangerous and painful situations, especially if someone is allergic to their stings.
     I happen to be someone who was allergic to Yellowjacket venom (though thankfully not to other stinging insects such as bees or paper wasps). In my case, I use to get stung numerous times a season. Though it hurt, I was not too worried about them. One day however, I was stung in the ear while at work at a nature center. After getting some ice and complaining to my coworker, I started feeling dizzy and then blacked out. I awoke in an ambulance and getting a rash and hives. After getting stung so often, though over time, my body had finally had enough getting envenomated. I had to go through a desensitization program of weekly injections until I had built up my resistance to their stings once more and still have to carry an epipen just in case. Interestingly, that was many years ago and I have not been stung since. I have a sixth sense it seems now in seeing their nests and avoiding them.

A Yellowjacket worker enjoys a sugary drink from a bottle cap.

     In the Fall is when we have most negative encounters. Not only are the nests large and there are more workers, but their behavior changes a bit too. Yellowjackets throughout the summer had to bring back food for the young and work to keep their nests in good shape. This included repairs, expansions, and keeping them dry. Workers of paper making nests have to sometimes drink excess water to keep the nest from getting destroyed after rains for example.
    By Fall however, new reproductives are being produced, the new drones and queens. There are fewer larval mouths to feed and many workers helping to do this. Many Yellowjacket workers thus go for the easiest food they can find. While their preference for sweets is usually satisfied with rotting fruit and nectar, many discover easy food near trash cans, picnics, and from our sodas and sugary confections.
     While I must say that I certainly am not crazy about Yellowjackets (and have every reason I think to not like them), I respect them and understand that they're beneficial and have a role in our natural world to play. I just take extra caution in my outdoor activities, especially this time of year.

Wednesday, September 2, 2015

Pawpaw

A nice clump of pawpaws nearing ripening under their huge, tropical-looking leaves. 

     North America's largest indigenous fruit is the Pawpaw, Asimina triloba, each attaining 3-6 inches in length when ripe. They are in the Custard-apple family Annonaceae, this genus being the Northern most members of this mostly tropical family. Like the Annonas and Cherimoyas I've eaten in Latin America, these too are quite edible. Their flavor is hard to describe, the consistency being like a banana, some people thinking they taste a bit like them, others comparing them to mangos and papayas. I don't think any of those is completely accurate though.

The Pawpaw is North America's largest indigenous fruit and the cold hardiest member of the custard-apple family. 

     Their most common name, Pawpaw or Paw-paw is thought to be derived from the word "papaya" with which they've been confused. They have numerous other names however, mostly due to their vague similarity to the banana: Wild Bananas, Michigan Bananas, Ozark Bananas, Hoosier Bananas, West Virginia Bananas, Kentucky Bananas, Prairie Bananas, Kansas Bananas, and Banango.

Flowers bloom when the leaves are still small and emerging.

      Pawpaws bloom in spring, usually just as their huge (up to 12 inches) tropical looking leaves start to grow. Being an understory tree or shrub, they need the large leaves to collect what little sunlight filters through the canopy. But blooming once the big leaves are out would obscure the flowers and interfere with pollination. Most of our spring blooming trees and shrubs thus do so when the leaves have not emerged or are just starting to grow for that reason.

The flower seen from underneath.

     The flowers are not your typical looking blooms either since they are attracting different types of pollinators. They lack the bright colors that many pollinators such as bees look for. Rather, they are likely pollinated by carrion flies, bottle flies, and carrion beetles. So they look (and often smell) like the color of meat: brown or maroon. They hang bell-like from the twigs, resembling the blooms of wild ginger, which often bloom underneath them at the same time and look a lot like them.
     Fruit set is often not very reliable. Not only do you need to attract unusual pollinators, but it is also believed that they are self-incompatible. Most of their reproduction is via suckers sprouting from the roots to grow a new tree. That means that a pawpaw patch may be all the same plant, all clones from the suckering roots. So you need pollen to be brought in from outside sources and you may get poor fruit set even with lots of flowers and a large colony of them. I've tried to hand pollinate them from the same clump and have not had good results.
     This, along with that the seeds may need 2-3 cold stratification periods (2-3 winters typically in the wild) to germinate, as well as that the fruits bruise and get over ripe easily, have made commercial production of this extremely cold hardy fruit problematic. People have tried (there's even a Pawpaw Foundation in Maryland trying to get commercial varieties that store and ship better) to make a business out of these, but have not often been successful. I've even heard of some people trying to keep orchards of pawpaw and hanging rotten meat when the trees are in bloom in the hopes of getting the right pollinators.

The flesh is soft and delicious, but does not store well and has large seeds.

     So production isn't easy. This is really too bad because the fruits are delicious! They are soft and juicy when properly ripe, with a strong tropical aroma. But getting them when just right and beating the wildlife to them is tough. Deer, bear, raccoons, possums, squirrels, mice, rats, voles, chipmunks, flying squirrels, turkey, and many other birds gobble them up. You need to wait until the fruit is a bit squishy, has a slight aroma, and is just starting to get yellowish with dark patches. Shaking a tree early in September around here sometimes results in a few good ones falling (and bruising themselves). They do not store well, especially if packed with other pawpaws or fruits which seems to make them ripen even faster. They might last a week if not bruised and refrigerated. A word of caution however, a small number of people have a slightly allergic reaction to the fruit skin, leaving a skin rash. My grandson falls into this category for example.
     The fruits also have a slight laxative effect, so take care how many you eat. A fellow naturalist related to me how he took scouts overnight camping one time and let them discover the joys of eating pawpaws. He warned them to just eat one or two apiece, but some of them, liking the pawpaws so much, harvested many more for use as night snacks, with predictable results.      

The large fruits have large seeds. Here's a handful from a single fruit.

     They have large seeds, but these are easy to remove. I often find them in the scat of other animals in the woods. They seem to sometimes be dispersed by the water as well, with most colonies growing near water ways.

Pawpaws have a golden Fall color, though the trees are short, they grow clumped together making for a showy look. 

     Though individual trees rarely get to 40', they are usually in clonal colonies. These pawpaw patches have yellow Fall color that makes them stand out. They also have fairly smooth, grey bark (though the older specimens get wartier as they age). The buds are also somewhat fuzzy, making them not too difficult to identify even in winter.

Pawpaw buds are hairy, which along with the smooth gray bark (sometimes a bit warty on bigger trees) make them fairly easy to identify even in winter.

The trunk of a Banango showing the start of the warts and bumps large specimen end up getting. 

     The trees have very large leaves that when crushed have a smell reminiscent of petroleum. Few things will actually eat the leaves (mules being one of them). This has resulted in their actually being one of the few native plants benefiting from the over population of deer we normally have in our region. They tend to eat other plants and seedlings first, selectively allowing pawpaws to survive better at least initially, though at the expense of other plant diversity.

The Michigan Banana is the sole larval host (food plant) for the Zebra Swallowtail Butterfly in our region. Here several males are puddling collecting salts and minerals. 

     One animal that really needs them though (other than for their delectable fruit) are Zebra Swallowtail Butterflies. Their caterpillars can feed on nothing else, pawpaws being their sole host plant. There are two species of Asimina (pawpaws) in the Northeast by the way, though the Dwarf (Small-fruited or Small-flowered) Pawpaw Asimina parviflora does not range into our DC region. Zebra Swallowtails are believed to retain some of the chemicals that make the plant distasteful and even toxic to other animals (mostly acetogenins) as a means of defense. You likely will never find these caterpillars on the pawpaws though, unless you visit the trees at night when the caterpillars climb out of the leaf duff and climb up to feed in safety from hungry birds. 
     The first European to note the use of the plant for food was DeSoto in the lower Mississippi in 1541. Since then many others have enjoyed them. It was claimed to be a favorite of George Washington who loved them when served chilled. Thomas Jefferson made sure to plant pawpaws on his plantation, and Lewis and Clark recorded eating them on their voyage of discovery, surviving off of them for 3 days. I've had both pawpaw bread and ice cream and can highly recommend them. Some enterprising folks have made jams and used them as substitutes for bananas in many dishes. I've even heard of wine being made from them, though have yet to taste that.
     Though  use of the huge fruits for food is obvious, there are many twists to their uses. The Iroquois not only made breads and cakes from them, but also sun dried the fruits for later use. The Cherokee not only ate them, but also used the inner bark fibers for rope, mats, and for stringing fish. 
     Francis Porcher, who wrote a Confederate treatise on using plants for many ethnobotanical purposes during the Civil War shortages, made some interesting notes on the use of the plant other than for food. Noting the chemical properties, he suggested using the juice from the unripe fruit to treat intestinal worms and the rinds to treat ulcers. He noted the poisonous seeds and how when crushed had been used to treat head lice. Porcher recorded that the leaves could be fed to hogs and poultry to tenderize them, claiming that freshly cut meat could be hung over the leaves to also tenderize them. The acetogenins that give the leaves their strong smell and make them distasteful to most wildlife are now being tested for use in treating tumors and as insecticides. 
     So you can see that there's a lot more to this plant than just its tasty fruit. But for me, that would be enough anyways. In 2009, Ohio declared the Pawpaw its official state native fruit. Not sure what took them so long, people have been enjoying pawpaws for such a long time. I know I look forward to visiting my favorite pawpaw patch very September. always trying to outguess the critters competing with me to get the Wild Bananas! 

My son Alex enjoys picking pawpaws almost as much as like eating them...