Wednesday, September 28, 2011

Parasitic Eulophid Wasps

For every creature that exists there seems to be something designed to control it or destroy it. Insects in particular have it rough. If it isn't enough that they must survive against onslaughts of pesticides and smack happy humans, they must also try to avoid the unavoidable, parasitic insects.

There are thousands of species of parasitic insects out there, but some of the most common are in the order Hymenoptera and are called wasps. The term wasp often brings to mind highly defensive komikazee insects that would just as soon sting you as look at you. While some wasps are highly defensive most are not, and the parasitic variety of wasps are completely harmless to humans. The only thing that need fear them are the insect quarry they are after. One particular group of parasitic wasps fall into the family Eulophidae. Wikipedia lists 4,300 species worldwide in over 300 genera. Several are plant parasites, but most are insect parasites. Each species has a preference for a host with many choosing caterpillars to lay their eggs on.

These are extremely tiny wasps at around 2 mm in size. They would easily go unseen by the human eye, if you weren't paying attention. In fact I can't say that I have ever seen an adult. The female will land on the back of the caterpillar, and use her sharp ovipositor to inject the eggs just under the surface of the caterpillars skin. She may lay dozens of eggs at a time on a single host. The eggs hatch in a few days and the young wasp larvae begin feeding on the caterpillars innards. For awhile the caterpillar will go about its daily business of munching leaves as if nothing is awry. Eventually, however the constant feeding of the wasp larvae will take its toll on the caterpillar and it will succumb to an early death.

Once the wasp larvae have reached full size they will emerge from the skin of the caterpillar and form cocoons. These fuzzy-looking growths are the cocoons of a eulophid wasp. It has a very fungus-like appearance. In fact when I first found this unfortunate victim I thought it was some type of fungus. Charley Eiseman who is an expert in this type of identification was able to assure me that this is indeed a type of Eulophid Wasp infestation on the caterpillar.

Then I ran across this individual caterpillar with a similar infestation. This one was attached to a blade of grass, and in addition to the fungus-like cocoons of the eulophid wasp there are also visible eggs near the head of the caterpillar. Charley felt the eggs were from some type of tachinid fly and were probably laid after the eulophid wasps had already destroyed the caterpillar.

These are highly specialized wasps and provide excellent control of potentially harmful insects. Many moths in the caterpillar stage wreck havoc on crops and cause billions of dollars in damage annually. These tiny wasps certainly do their part in minimizing the damage these caterpillars inflict. They are so good at what they do that many species are being reared and released in areas where certain pests occur in large numbers. This is biocontrol at its finest. I am a firm believer in using what God gives us to control problem pests, rather than relying on manmade chemicals that have questionable outcomes on the environment.

Sunday, September 25, 2011

Ground Sac Spider

This multi-colored beauty has been identified as a Ground Sac Spider (Genus: Trachelas). This particular specimen is a female and she made her way into my in-laws house and managed somehow to make her way into my father-in-laws shirt unbeknownst to him. While trapped between the shirt and his back she bit him. He shook his shirt out to see what had bitten him and discovered this spider. He was concerned it could have been a brown recluse so he captured her and brought her to me to be identified. I was able reassure him that it definitely was not a recluse, but I had no idea what it was beyond that. It left a nickel sized welt on his back that itched for about 2 hours before disappearing. After posting this picture to facebook Mandy was quick to respond and provide a positive ID. When I mentioned that the spider bit my father-in-law she seemed shocked that this spider would bite anyone and considered it extremely rare that it did. The venom from this spider is harmless to humans and is designed to subdue their small insect prey. This spider commonly enters homes, but generally speaking it is the males that do so. Joe Lapp another spider expert explained that these are wandering spiders and the males are on a mission to find females. This quest to locate mates often leads them into homes by mistake. He even created a cartoon that aptly describes this misguided behavior. In the cartoon below the male ground sac spider aimlessly wanders around, in and out of this house seeking his quarry before finally finding her in a cherry tree.

Joe has a wonderful website full of cartoons that humorously describe the behavior of spiders and their relationship to humans. To read more of his cartoons please visit his website Spider Babble.

Joe pointed out to me that the common name of "Ground sac spider" is probably not the best descriptive name for this genus of spiders as some species are often found in trees. Trachelas tranquillus are commonly found in leaf litter on the ground so this is probably what earned them their common name.  Also, I see that some web sites are referring to this species (or genus?) as the Broad-Faced Sac Spider, which seems like a good name to me.These spiders are also considered ant-mimics and looking at this particular specimen I can see how that would be the case. They are rather ant-like in their appearance.

Identifying spiders is often a challenge even for the experts and often requires microscopic investigation of the genitals before an accurate ID can be achieved. Having learned this bit of information from several spider experts I always try to make sure to photograph the underside of the spiders I find. This is often a tricky endeavor and requires patience as spiders apparently do not like being on their back. I flipped this little gal over several times with a dried piece of grass before she finally seemed to realize I was not going to stop flipping her until she laid still. After several seconds of motionlessness I was able to snap 4 or 5 pictures before letting her right herself and wander off.
Mandy said that in many cases a photograph is enough to identify to species, but in the case of this particular spider there are two species that are so similar that it requires microscopic inspection of the genitals. She felt pretty confident that it was T. tranquillus which occurs almost state wide. There is an additional species found in Missouri, but it traditionally has been restricted to the southern tip of Missouri. There is a slim chance it could be this southern species as population ranges do change year-to-year, but I feel pretty safe in saying that it is indeed T. tranquillus.

Friday, September 23, 2011

Giant Grassland Cicada

Prairie Cicadas (Tibicen dorsata) are a large and very common cicada in Missouri as well as throughout the Midwest. They are beautifully marked with caramel and black. The wings are deeply veined and held over the back. These insects are powerful fliers and sound like military bombers as they buzz by your head.

Males call loudly from the trees or other vantage point. They are using their best Sinatra serenade in the hopes of attracting a nearby female. Males who sing the loudest and proudest are sure to gain the privilege of mating with the most desirable of the local females. Once mated the females will lay their eggs on or near trees. When the eggs hatch the nymphs must find their way underground where they will remain for one to two years feeding on the roots of trees, shrubs and other vegetation. Damage to plants and trees is minimal and is not likely to cause any noticeable problems. The adults reportedly feed on the sap of trees and plant juices. 

These insects are often called Locusts, which is truly a misleading term. Locusts are actually a type of migratory grasshopper that are famous for forming extremely large swarms that devastate crops and grasslands. In the United States the Rocky Mountain Locust was responsible for mass destruction of prairies, cropland and other vegetation during the 1800's. The last specimen found alive was in 1905 somewhere in Canada. Africa still wages war with locusts each year, and DDT is still widely used in an attempt to control their devastation. 
Cicadas are not closely related to grasshoppers at all, in fact they are in the order Hemiptera and are more closely related to leaf hoppers, or even stink bugs than they are locusts.

This particular species of cicada is also known as a Dog-Day Cicada, and are so named because of their appearance during the hottest days of summer. The songs of these creatures from high in the trees is synonymous with summertime. All too soon their song will cease and the brisk fall weather will be upon us.

Wednesday, September 21, 2011

Crabby as a spider

I apologize for being so lax in getting stuff posted here lately. My life seems to be in overdrive at the moment. My husband had a bout with Salmonella and ended up in the hospital with severe dehydration and nearly died. My son bought his first house and moved out which required our help and messed my own house up from top to bottom. My daughter got a DWI after leaving a friends wedding. Once we got all that stuff resolved, she went to a concert and got an M.I.P. So I am back to being mom-taxi and trying to get her back and forth to college, plus trying to do my own job. Then to top it all off this past Saturday Joey and I were in a bad car accident on the highway. Thankfully no body was seriously injured, but I sustained some severe bruising to my sternum which hurts every time I move. The past 6 weeks have been chaos to say the least. I am looking forward to some much needed calmness in my life. All this drama is enough to make a person crabby.
I guess the old saying holds true "When it pours!"

When trying to decide what to write about in this post I kept coming back to one of my favorite creatures in the garden and that is the crab spider. The name sure fits my mood lately! These spiders helped me overcome my arachnophobia and cured my life long fear of eight-legged creatures. These are small, unassuming, almost comical spiders that rest on flower blooms waiting to ambush unsuspecting insects. Like most spiders their life begins in the spring after emerging from the egg sac their mother so lovingly formed the previous fall. They will be impossibly tiny and often go unnoticed among the flowers for many weeks. As they eat and grow we begin to spot their curious-looking little bodies sitting motionless among the foliage and flowers as if they have all day to just hang around.

(A juvenile crab spider hidden inside a red tulip--photo taken in April)

There are many different species of crab spiders, but the majority of the ones you will find in Missouri will be flower crab spiders. They get their common name from their preference for hanging out in flower blossoms. This is a perfect adaptation...what better place to hang out when seeking your food of choice....insects? We all know insects are attracted to flowers, so these guys go where the source is and wait for a passing meal to come. They won't have to wait long, and with such a ready supply of food they grow quickly and generally reach adult size by the first of August.

They  aren't picky about their diet, any six or eight legged creature will do. 

As the following pictures will show.

(Crab spider eating a fly)

(This tiny crab spider caught and devoured this much larger flower fly)
(Flies must be tasty)

(Here a crab spider found a tawny-edged skipper to her liking)

(Feeding on a Silver-Spotted Skipper)

 (This one is dining on a red Admiral Butterfly, talk about eyes bigger than your belly...geesh!)

Crab spiders are amazing in other ways too, many of them can change color to blend in with their surroundings, this is using camouflage to the utmost advantage. If you are white and sitting on a white flower you will most likely go unnoticed.....or lets say you're sitting on a pink and white flower....why not add a little pink to the disguise?

Yellow Flower?

These spiders even entertain themselves when they are not out searching for food or mates....How about a rousing game of piggy-back ride?....or is it leap-frog?

Many crab Spiders participate in Olympic pole vaulting...just look at this form and grace!

Crab spiders are expert hunters, and often capture and consume prey much larger than themselves. They are not known to bite and are excellent spiders to handle. They come in a wide array of colors from brown to pink and white. I am constantly on the look out for these spiders among the flowers. This time of year they are most noticeable because they have attained their full adult size and will usually be seen with some sort of prey protruding from their front fangs.

Tuesday, September 13, 2011

Rattlesnake #4----It's a Boy!

Sunday we drove to the farm to set out some turtle traps in the hope of capturing a common snapping turtle to use for a program we are giving at work Tuesday evening. After wading into the pond and setting both traps we headed to the local diner for lunch. We had just pulled into the parking lot when my brother-in-law called and said they had a timber rattlesnake captured in the shed on another farm (where we had previously tagged several). Joey and I immediately left the restaurant and headed to the farm to see the snake.

We pulled in to see Tony holding the snake inside this fish net. It was not rattling or trying to strike. It seemed fairly calm. We released it from the net so I could take come pictures. After photographing it we placed it in a plastic barrel for safe keeping until I could contact Dr. Mills and have him meet us at the farm to document the snake.

This snake had recently shed its skin  and was as bright and shiny as new coin.

Tony (my brother-in-law) and Jimmy (my father-in-law) were determined to make sure the snake wouldn't get out of the barrel. The measures they took to keep it contained made me laugh. It looks like they are trying to contain an anaconda instead of a 3 foot rattlesnake! I believe this snake will remain in the barrel until we remove it. Once in the barrel it began rattling in earnest, and the sound of it in the barrel was magnified making it sound like a box full of cicadas. The first time I heard a rattlesnake vibrate its rattle I was stunned at how much it sounded like a cicada. In an area where cicadas are plentiful and rattlesnakes occur it can be kind of freaky. Your mind will play tricks on it a cicada? it a rattlesnake? Then you begin looking around to make sure you aren't about to step on a snake hidden in the grass.
Once everyone was satisfied that the snake wasn't going to escape we left and headed back to the diner to eat lunch. After enjoying a tenderloin and fries we headed home and I still could not contain my excitement over the rattlesnake. I think I tried calling and emailing Dr. Mills at least 5 or 6 times. I simply could not wait to tell him about the snake. He returned my call and agreed to meet us bright and early the next morning.

 I arrived at the farm at 7:40 AM to find Jimmy and Tony already there. Dr. Mills and Cindy arrived shortly thereafter. We peeked in the barrel and our captive was still present and accounted for, but unfortunately the stress from his capture and incarceration caused him to regurgitate two partially digested mice. I felt bad that we caused him so much stress, but I also knew the data we would obtain from this snake will be invaluable in gaining more knowledge on this misunderstood and often vilified creature.

We removed the snake from the barrel and quickly contained it inside a clear tube. It was remarkable how fast we were able to tube this snake, it normally takes numerous tries to coax them in, after just two attempts it was safely secured.

(right after getting the snake in the tube we measured it. 
It measured 99cm or just over 3 feet in length)

(Here we are preparing to hand the snake over to me)

(Scanning the snake to see if it is one we had previously pit tagged. No BEEP, so it is a new snake. He probed the snake and we happily discovered it is a male. We know he has at least three females nearby, so hopefully he is breeding his little harem)

 (The snake is trying really hard to back out of this tube, it is amazing how strong their muscles are. Right after this Dr. Mills inserted the pit tag.)

(Here we are bagging the snake to weigh it---it weighed 1000 grams, or just over 2 pounds)

(We carried the snake about 100 yards away from the shed and let it go on a concrete slab that has a lot of rock piles and other places to safely hide)

In four months we have found 4 rattlesnakes on this farm. Each one has been in the vicinity of the shed and corn crib which is approximately a 150 yards radius. We are curious to know where they are hibernating. We plan to radio tag one before the season ends and they all go underground for the winter. We will be able to gain much more knowledge about their habits and habitat with this additional technology. Ultimately we want to be able to protect their winter locations and perhaps locate gravid females. 

The fears and stigmas associated with this species of snake ultimately leads to many unnecessary deaths. Ignorance breeds fear! Often if we can reach out to people and share our passions we can change attitudes. I am proof that it works. My in-laws used to kill every rattlesnake they saw, now they are helping preserve them for future generations! 

Thursday, September 8, 2011

Zombie Moths? Insect Slavery? Invertebrate Body Snatchers?

Zombie Moths? Insect Slavery? Invertebrate Body Snatchers?

The stuff of nightmares? Perhaps if you are a gypsy moth.

This sounds like the newest sci-fi thriller , instead it is a reality playing out in a forest near you! Jenny M. Seifert sent me this article and I thought I would share it with you readers. This is fascinating stuff!

Thanks Jenny!


Viral enslavement

If you think slavery has been abolished, consider the case of the gypsy moth and the virus. For more than 100 years, people have noticed that some gypsy moth caterpillars climb to the top of trees before they die and decompose, or “melt.”

Dead caterpillar hangs on a tree in a u-shape, oozing liquid
Image courtesy Michael Grove
Dead gypsy moth caterpillars liquefy, releasing infectious virus particles.
Melting releases more virus particles and is the normal fate of these caterpillars, but why did only some caterpillars perform this ascending death march?
Gypsy moths are voracious insects that have been spreading across the United States for a more than a century, so nobody is feeling too sorry for them, especially people who have seen them strip forests bare.
Still, it’s nice to read a good explanation for this peculiar “climb, croak, melt” behavior.

All the better to infect you with, my dear!

A study published today identifies a viral gene that blocks one stage of maturation in gypsy moth caterpillars, which normally hide during the day. But when Kelli Hoover, a professor of entomology at Penn State, and her colleagues infected bottled caterpillars with the virus of doom, the caterpillars showed the same climbing ‘n’ dying behavior that appears in the field.
Images courtesy Michael Grove
Healthy gypsy moth Lymantria dispar caterpillar on a leaf. Roll over to see a female with her egg mass. Female gypsy moths, which do not fly, can pick up the virus from tree bark and infect the egg mass under her wings.
In nature, those caterpillars would melt and then rain virus down to infect other gypsy moths.

The moth misbegotten

Gypsy moths were introduced to Massachusetts in the late 1800s by a bumbler who wanted to raise silk by crossbreeding them with silkworms — a different species, says Hoover. “It was crazy; this guy did not know anything about species, apparently.”
Still, the gypsy moths did bring fecundity and a ferocious appetite to the table — or forest. “They eat so many different kinds of trees and plants … in a bad outbreak, the insect frass dropping down sounds like rain, so you need a hat,” Hoover says.
We had to look it up to be sure, but frass is basically insect poop.
Gypsy moths are such effective defoliators that authorities try to control them with Bt, a bacterial spray that unfortunately kills beneficial insects, not just harmful ones.
Hoover’s study focused on a viral gene called egt, which inactivates a hormone that starts molting – a process that ends each stage, or “instar,” of the caterpillar’s development. “When they stop molting, they keep feeding, and that’s why we looked at egt,” Hoover says.

Two men with horse-drawn tank and upright heater-sprayer in front of a brick house
Photo: USDA APHIS Pest Survey Detection and Exclusion Laboratory
The battle against gypsy moths was joined before 1900, when an unknown chemical was sprayed against the invader.

The study compared the behavioral effects of:

two normal strains of virus;
two strains with a busted egt gene, and
two strains with a restored egt gene.

A dangerous meal

In every case, Hoover says, “if the gene was active, the moth died at the top of the bottle. If the gene was inactivated, it died at the bottom.”
It’s not clear, Hoover says, exactly why the gene changes behavior, but this is the first time it was traced to a single gene.
Caterpillar at the bottom of one bottle, on top of another bottle
Image courtesy Michael Grove
These soda bottles contained a screen and a caterpillar; insects infected with a virus containing the egt gene climbed to the top before croaking; others croaked down low.
Because LdMNPV (the Lymantria dispar nucleopolyhedrovirus) infects only gypsy moths, and kill them at a young age, it might work as a biocontrol agent against a disastrous insect invasion. However, Hoover says, “the experiment’s goal was more basic – to understand how the virus enslaves its host.”
Certainly there is evolutionary logic behind changing your host’s behavior for your own benefit, assuming you are a pathogen or parasite, and “body-snatching” is well-known. For example, a fungus forces ants to climb, zombie-like, and die where they can easily spread fungal spores.

Tree-covered mountains, the trees on the mountain in foreground are stripped of their leaves
Photo: rjcox
Gypsy moths defoliated Virginia’s Shenandoah Valley in 1990.
And it’s not just insects. The rabies virus, Hoover adds, “causes dogs, raccoons and bats to become more aggressive, to be out during the day, where they approach people and try to bite them,” which spreads the virus even though it endangers the animal.
And toxoplasmosis, a parasite, can make mice less fearful of cats, Hoover says, “so they are more likely to get eaten and infect the cat.”
There is even speculation that toxoplasmosis may cause men to behave with greater jealousy, Hoover says, “but the only thing that’s really been looked at is that mice with toxoplasmosis have a higher level of dopamine,” a feel-good neurotransmitter.
Is slavery therefore not all drudgery?
— David J. Tenenbaum

Terry Devitt, editor; S.V. Medaris, designer/illustrator; David Tenenbaum, feature writer; Amy Toburen, content development executive; Jenny Seifert, project assistant

Wednesday, September 7, 2011

Pipevine Swallowtail

Pipevine Swallowtails (Battus philenor) are gorgeous butterflies native to North and Central America. With a wingspan of 3 1/2 inches they are a large black swallowtail with beautiful iridescent blue hindwings. Males have more blue on their wings than females. They have seven orange spots on the underside of the hindwings. While these butterflies can occur in a wide variety of habitats they seem to favor forested areas. The one photographed here is a male that was perched high in a tree. I assume it was waiting for a passing female to mate with.

Much like monarchs that feed on milkweed which gives them protection from predation, this species also feeds on toxic plants. In the case of pipevine swallowtails they feed on plants in the Aristolochia family which are pipevines, dutchman's pipe and birthworts. As they feed on the plant in the caterpillar stage, they take in the toxins of the plant making them unpalatable to would-be predators. Like monarchs they will be toxic in all stages of life from caterpillar to adult.

The adults nectar at a wide variety of plants including thistles, bergamot, lilac, azaleas, teasel, phlox, petunias, lantana, verbena, and butterfly bush to name but a few. If you want to attract these butterflies to your yard, first make sure you are in an area where they are known to occur, then plant the host plants. Host plants provide nutrition to the caterpillars and with most butterflies being plant specific in their needs, the female will be looking for suitable host plants to lay eggs on. Most any nectar plants will suffice to attract butterflies.

Many species of butterflies have adapted coloration similar to the Pipevine which affords them a certain amount of protection from predation. The dark phase of the Eastern Tiger Swallowtail, The Black Swallowtail, The Ozark Swallowtail, Spicebush Swallowtail, Red-Spotted Purple and the Diana Fritillary all take advantage of the defense implemented by the pipevine.

Friday, September 2, 2011

You know its hot when........

3/4 of our summer has been extremely hot with temperatures well over 95 degrees and heat indexes over 100 degrees. This little eastern fox squirrel found relief from the heat on the concrete deck outside my office window. He stretched himself out and cooled his belly off on the shady concrete. He stayed there for nearly an hour panting. I took a picture through the screened window, since I was afraid opening the door would have spooked him. This was a true indicator of the heat we've been experiencing.

Thursday, September 1, 2011

Silver-Spotted Skipper

Silver-spotted skippers(Epargyreus clarus) are without a doubt the single most widely seen butterfly around the Midwest. When I photographed these butterflies there were no less than 20 or 30 of them nectaring at the zinnias.
They are quite large for skippers and have a wingspan up to 2 5/8 inches. Their color is a distinct all over chocolate brown with bright white (or silvery) spots on the underside of their hindwings. Forewings have golden spots.

The adults perch on the underside of leaves during the hottest days of summer and at night. During milder weather they will nectar at a wide variety of flowers, but seem to prefer flowers colored red, pink or purple. Rarely will they nectar at yellow flowers. They can be found in flower gardens, near woodlands, and in open fields.

Males perch on tall plants and wait for passing females, occasionally they may patrol seeking females with which to mate. Some experts claim that once mated the female will lay single eggs near, but not on the host plants. Caterpillars must find their own way to the host. Other experts argue the opposite and claim they lay their eggs on the host. So it depends on who you ask or what resource you use.  Host plants for the caterpillars include Honey Locust, Black Locust, False Indigo and various other Legumes such as Glycyrrhiza and wisteria as the one pictured below was feeding on.

The caterpillars rest inside rolled up leaf shelters that they create by silking together leaves. They will regurgitate a greenish colored, bitter-tasting chemical defense when disturbed. The sphecid wasp, Stictia carolina, also sometimes provisions its nests with silver-spotted skipper larvae. Frass (insect poo) is often a sign to wasps that the caterpillars are present....therefore the caterpillars have the ability to project their frass great distances in order to not advertise their presence to would-be predators. I've heard of projectile vomit, but projectile poop? How ingenious! When the caterpillars are ready to pupate they will remain inside the leaf roll and form their chrysalis. They overwinter in this stage.