Life on a leaf-Braconid

When I find signs of life on a leaf, it usually follows me home.  Stored on our table (thanks, Barb) it can wait weeks before there is an answer, if any. Here are some examples.  A yellow spot on the underside of a maple leaf turned out to be eggs.  I stored them on August 24th and expected to see some larvae emerge but when I checked them on October 17th we had lots of little adult bodies gone past their prime.





Chris Barnhart explained that they had been moth eggs laid in a cluster, possibly oakworm moth eggs of Anisota spp.  Instead they had hatched parasitoid wasps, likely chalcid wasps.  These are parasitoids attacking the eggs or larvae of a large number of insect families.  They tend to be black or brown, often metallic, and have reduced veins in their wings.

Barb brought in this leaf of kale from the garden with cocoons attached.  They soon hatched out these tiny wasps.

Chris explained that they are braconids, probably Cotesia.  They have a distinctive black stigma on the forward edge of their wings.  The larvae can choose to leave the caterpillar entirely and cocoon in a mass.  Bugguide has several examples of these cocoon collections with no evidence of the parasitized larvae left.

Braconid wasps - Microgastrinae - Joy Markgraf 

If you like raising tiny insects and have an understanding spouse or roommate, wasp parasitoids may be for you.  Start looking on leaves.
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A number of you have mentioned the late Monarch migration we witnessed this year and asked what it meant for the population.  Here is the opinion from the expert from Monarch Watch.

Aphids on a Dock

On the MN training field trip to Henning Glade, Becky Swearingen and others found a prairie dock, Silphium terebinthinaceum, flower head covered with orange dots.  These were aphid larvae with an occasional adult, crawling all over the stem.  In the middle of the scramble there was a long flat area with a lot of "stuff" on it.  On closer inspection, this was the protective cover on the back of a debris-carrying lacewing larva.



We described these lacewings in a past blog but I took this one home with me for pictures.  When I opened the little insect box the next day, it was a scene of aphid carnage.  There were over 30 aphid carcasses scattered about, sucked dry by the lacewing larva.  It was interesting that during the feeding orgy within the confines of the little box it hadn't made any attempt to decorate its back with debris as it had the day before.

There are several possible explanations for this "naked" lacewing.  Some aphid colonies are protected by ants in a symbiotic relationship.  The ants get aphid honeydew and the aphids get protection from bullies like these lacewing larvae.  Thomas Eisner removed debris from some of their backs and showed that decorated lacewings could invade an aphid colony while naked ones were repelled.  It may also be that the day before it was just covered by crawling aphids.

Our Master Naturalist videographer Linda Bower has this clip showing a green lacewing larva grabbing an aphid (at :32 seconds) and then sucking away, earning its name as an aphid lion.

Horntail Technology

 
This insect caused quite a stir when found on a tree at the WOLF playground because of its prominent "stinger."  Although it looks dangerous, it is actually harmless unless you happen to be a tree.

Wasp stinger with venom drop - Wikipedia CC

This is a horntail wasp of the Siricidae family, another example of a wasp without a stinger.  The 20,000 plus species of solitary wasps do not have stingers.  Social wasp females such as the yellowjacket have their ovipositor modified to sting defensively, delivering a dose of venom to remind you of it for longer.

Horntail and ovipositor - Barry Stewart

Siridicae's "horntail" seen above is really decorative, of no known purpose except to scare us.  The female's ovipositor is beneath and much more flimsy looking.  It uses it for the original purpose, in her case injecting an egg into wood.  Imagine the pressure required to push a pin or needle into wood and compare it to the lightweight wasp body.

Urocerus albicornis - Eric Adams

The ovipositor overcomes the weight problem by mechanics.  First, the ovipositor lies inside a sheath that absorbs most of the pressure.  She will probe the wood in several places, finding a soft spot to inject the egg with fluid.  It contains a fungus that she carries in an abdominal opening.  The fungus will attack the wood while the egg matures, providing the newborn larva a predigested meal. 

Ovipositor with sheath on either side - Stanislaw Kinelski, Bugwood.org CC

The story gets even better.  Many species of horntails have zinc in their ovipositors as well as in the adult's jaws, hardening them for chewing out of their wood incubator when they emerge as discussed in this previous blog.  In addition, the horntail ovipositor design has inspired new medical instrumental technology as described in Materials World Magazine:

"The wood wasp’s ovipositor looks like two hollow needles, one inside the other, each of which is lined with backward-facing teeth to give purchase as the wasp ‘drills’ progressively into the bark of a tree. This takes surprisingly little force, making it attractive for carrying out minimally invasive procedures such as brain biopsies without having to exploit a natural orifice."

The only significant damage they cause is if a board used in your house construction contains the larva.  When the adult emerges from its pupa it will chew its way out through wood, plasterboard or even a plastic covering.  Please forgive it and understand what a cool insect is visiting your house.
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More at blogs by Bugeric and the Bug lady.

Asian Ladybugs

This story starts with an inquiry from Lori Herring and her 2nd and 3rd grade students at Marshfield R1 School.  They were studying trees and found the maple leaf above with something on it they couldn't identify by field guides.  A first guess was an Asian ladybug larva but there was more to the story.

Early larva

Zooming in you can see a little beyond halfway down that the larva is splitting its skin down the back to expose the pupa.  Notice the spiky features at the front, the remains of the last larval stage to the right.  This is the last step in its metamorphosis before it emerges in the fall to start to torment us.  Arkinspace.com describes this step in the life cycle: 

"When the larva has grown to its full size it will then attach itself to the stem of a plant. It splits along its backside and exposes the pupa underneath. This sounds like something out of one of the “Alien” films and it really doesn’t take long to figure out that they didn’t get those ideas straight out of their imagination! The pupa, though, is wrapped up in this final stage of its metamorphosis and so is safe from the elements – but not from predators. It is at this stage it is at its most vulnerable. If approached close to its hatching time by a possible predator it will shake itself dementedly to try and warn off the unwelcome visitor! This last stage takes just a few days and then the adult ladybug is ready to emerge."

Larval stage

Now back to the "torment."  This is the Asian ladybug, Harmonia axyridis, actually a beetle as all "ladybugs" are.  It is most commonly known as the harlequin, multicolored Asian, or simply Asian ladybeetle in the Coccinellid family.  Unlike our "ladybugs" beloved in children's stories and merchandise, these are no "ladies."

Last week, shortly after the first hard freeze of the year we had the sudden return again of swarms of these ladybeetles on the sunny side of the house, the trees and my neck.  There are those annoying little nips on the neck and arms and when I swat or brush them away I am left with a stink on my hands.  Why now?  Tim Smith answered the question in the Missouri Conservationist Ask the Ombudsman column several years ago.

"Each fall, during a warm-up following the first cold weather, the insects gather on the sunny sides of houses and other structures as they look for cracks and crevices where they can find shelter from the coming winter.  Many will survive the winter and appear again in the spring as temperatures warm and they try to exit the house."

According to Wikipedia, they were brought to the United States in 1916 to control insect pests of plants, but were not successful.  In 1988 they were observed in numbers in New Orleans, and since then they have spread.  By 1995 they were occasionally found in the Midwest and became common in 2000.

They cluster by the hundreds in protected spaces

Subsequently, they have also contributed to the decline in native ladybugs, presumably by out competing them.  They also have reached pest status to the higher biped mammals, i.e. us, both because of the swarming numbers, their little bites and unpleasant odors and the tendency to move into our buildings.  For information on these pests including control recommendations, check out this Ohio State site.
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Arkinspace.com has detailed photographs of their various life stages from egg to annoying adult.

This is a Bug?

Green Stink Bug

A student found this on the WOLF School field trip to Bull Mills and announced "I caught a mosquito!"  My first guess was crane fly, but I wasn't even close.  This is a stilt bug, aka thread bug, a member of the Berytidae family of Hemiptera or true bugs.  With their slender bodies and thin legs I would never have guessed they are related to other Hemiptera like stink bugs.

In addition to their svelte physique they have several distinguishing characteristics.  Their femurs (the leg segment nearest the body) have a swelling at the distal end.  Also their antennae are geniculate (elbowed - your word for the day) and have a slightly bulbous tip seen below.

Very little is known about their habits.  Although they are said to be common on plants in the spring, most are less than a half inch long, have little color and move slowly so they are hard to see.  While many are thought to be plant eaters, especially those plants with sweet hairs, some may be omnivores, eating plant bugs and their eggs.*

Despite the mosquito-like appearance they don't sting, bite or land on us deliberately.  Incredibly, they are said to overwinter as adults, without a drop of insulating fat on their body!  Googling 80 links didn't bring up any more details so I suggest you simply enjoy the pictures.

* The Bug Lady at UWM.edu Field station
 Shelly covered them at MoBugs in 2010.

Rotting Log Exploration

The WOLF students were exploring rotting logs at their Bull Mills field trip.  The most exciting find was several northern black widow spiders, Latrodectus variolus, with their typical disconnected hourglass on the ventral abdomen that we discussed in this September blog.  They also found a few smaller black spiders with orange and white markings.  I have submitted these to Bugguide and am awaiting a definitive reading but I suspect by their size and coloration that they are sub-adult males as seen at this link.

"The mature males are much smaller with abdominal markings that are more red-orange and either continuous or broken red-orange strip bordered by white down the dorsal midline of the abdomen. It also has several pairs of white stripes along the sides of the abdomen. Juvenile females can show a similar pattern of the mature males." Tarantulaspiders.com

False Wolf Spider, Zoropsis spinimana

There were lots of spiders crawling around in the wood and not all had eight legs after encountering the students' tweezers.  The spider above which I am calling a false wolf spider, Zoropsis spinimana, was as patient as a fashion model, letting me get views from all angles.  The image on the left was the exuvia of a spider, the skin it shed after molting.

Polygyridae snail, immature

Snails are common in rotting logs where their rasp-like mouths can scrape up fungal mycelia.  Chris Barnhart identified this as a pulmonate (air-breathing) snail in the Polygyridae family.  It is immature and measured only 10mm and spent the afternoon crawling laps in the Gerber babyfood bug box.

A final bonus was Mrs. Reece's find of this Halloween special, a marbled orb weaver.  These normally have a firm round abdomen but this one had just concluded her egg laying and was crawling through the grass displaying her new slim and dimpled physique.

More of their finds are at this link.