Little things that run the world: Parasitic Wasps

The parasitoid wasp Telenomus podisi emerging from Euschistus servus stink bug eggs.  The wasp is about 2 mm in length. As she developed, she consumed the bug inside the egg.  Both the wasp and the host stink bug egg are native to the Eastern U.S.

Parasitoids differ from other parasitic organisms in that they kill their hosts as a normal part of their life cycle.  Because many are quite small they often go unnoticed, however, their degree of importance in ecosystems far outweighs their diminutive size.  Parasitoids can be important for controlling populations of their hosts, and as such they can be great drivers of evolution of defensive behaviors and forms:

Defensive behavior: A Costa Rican stink bug in the genus Loxa defends her eggs by standing over them.  She will use her hind legs to deliver a sharp kick to any intruders; enough to startle a human or send a small parasitoid careening through the air.

Defensive form? All stink bug eggs have micropylar processes - a ring of tubes that allow sperm and oxygen to enter the egg.  Those of Podisus maculiventris are very long, forming a spiky crown around each egg.  I wonder if they serve an additional purpose in interfering with the movement of small parasitic wasps among the eggs.

Because parasitoid wasps are so effective at reducing populations of their hosts, they can be very useful for providing control of pest species.  When one organism is used to control another, this is termed biological control.  Current research is investigating certain parasitoid wasps as potential biological control control agents for the brown marmorated stink bug.

The brown marmorated stink bug is a familiar pest because of its annoying habit of hiding out in houses during the winter months.  Unknown to many, it causes huge losses in agricultural systems and negatively affects the environment; farmers must spray more pesticides to control stink bugs.  Researchers hope parasitoid wasps in the genus Trissolcus (a relative of the Telenomus wasp pictured above) will be able to provide control of the brown marmorated stink bug, without being a hazard for native stink bugs and ecosystem function.  Because of the close relationship that many parasitoids share with their hosts, many will not attack other species.

Halyomorpha halys, the brown marmorated stink bug.  Originally from Asia, this insect is a serious agricultural pest and a nuisance pest in buildings.  It is broadly distributed and has a growing range in the U.S. and worldwide.

Way to go...

Stiretrus anchorago the Anchor Stink Bug, in copula, with a twist.

 The anchor stink bug is a predatory pentatomid species that is found in Delaware, but looks very little like a stink bug at first glance.  While taking care of a lab colony of these bugs this mating pair caught my attention.  I was soon amazed to see that the female was upside down, or I suppose she was right side up depending on your perspective.  I soon realized the cause of this bizarre mating arrangement:

um, was it good for you?

That's right - I'm not sure this was a consensual act, or perhaps accepting this male was the female's last earthly act.  Either way, this is the first incidence of insect necrophilia that I have ever witnessed.  I suppose that wont do much for the male's reproductive success - especially if this is indicative of his mate preferences in the future.

Stink bugs are CUTE!

Edessa florida nymphs just after hatching

The talented Alex Wild at myrmecos.net posted what he suspects is the cutest wasp ever.  That may be so, but I think that these first instar Edessa florida stink bug nymphs are face-meltingly adorable.  What do you think, is the wasp cuter?

E. florida is one of our native pentatomids; not the introduced brown marmorated stink bug (Halyomorpha halys) that invades homes and destroys crops.  Some researchers think that stink bugs acquire an important first meal by feeding on fluid in their eggs or the glue that attaches the eggs to a leaf.  I have not seen any research to support this hypothesis, but it would be an interesting explanation for why they stick around after hatching.  Either way, I think the stink bug huddle may give them an unfair advantage in the cuteness department.

A native stink bug

Brochymena on Juglans

Brown Marmorated Merry Christmas!

This (not-so) Brown marmorated stink bug (Halyomorpha halys) was encountered during the Christmas display setup at Longwood Gardens.  This bug had been overwintering among decorations in a barn.  While the ornaments were being painted silver, it was found crawling away with a new festive look.

For me this photo marks the beginning of a new adventure.  In 2012 I will be working with the USDA on biological control of Bown marmorated stink bug.  The bug was introduced from Asia to Pennsylvania in 1998, and is well known in much of the United States as a Autumn home invader.

Halyomorpha halys finding its way inside

Many people do not realize that this indoor nuisance is a serious agricultural pest of soybeans, corn, fruit trees, and other crops.  In 2010 Pennsylvania stink bugs caused an estimated 25% crop loss in apple orchards.  The USDA is evaluating several species of wasps that attack stink bugs to determine if they are effective against the pest but safe for other organisms.  More on that to follow in the coming year.

Incidentally, silver spray paint works as a feeding preventative but does not quickly kill stink bugs, leaving me ample time to take photographs.  It did eventually die, prompting the declaration that it was 'the ghost of Christmas pest.'