2014. október 6., hétfő

A parasitic Trichopoda fly killing southern green stink bugs arrives in Hungary

... or so I think.

Alternatively, another tachinid fly parasitizing pentatomid bugs in this area (such as Ectophasia crassipennis shown in the picture below) must have acquired a taste for Nezara viridula recently. Considering the increasing number of N. v. nymphs all over the countryside, either possibility is good news for gardeners.

Ectophasia crassipennis, a tachinid fly parasitizing e.g. the pentatomid bug Palomena prasina
(Picture taken in Törökbálint, Hungary, August 9, 2014.)

So here is why I believe that the southern green stink bug is parasitized by a tachinid in our area.

I spent a lot of time last summer on taking pictures of the various instars of the southern green stink bug (Nezara viridula) in my garden. I was simply enchanted by their beautiful colors.
An adult stinkbug and a beautifully colored 5th instar nymph.
(Picture taken in Törökbálint, Hungary, July 13, 2013. See my Flickr album for more pictures of the bug.)
I also took a number of pictures of an adult sitting on the purple leaf of a bush of ‘Orange Rocket’ Berberis because I liked the color contrast. None of the images turned out sharp enough, but I had not discarded them nonetheless because of the two oval specks on the back of the insect, which had escaped my attention while taking the pictures. I thought they might be mites, but I could not see any legs and the color was also uncommon for a mite, which puzzled me.

I took this picture in my garden last year, on July 13, 2014. I believe, the two oval specks on the back of this adult stinkbug are parasitoid eggs, probably those of  Trichopoda pennipes
(Picture taken in Törökbálint, Hungary, July 13, 2013. See my Flickr album for more pictures of the bug.)

This year, I have been trying to organize the thousands of pictures I have on insects, spiders and the like, and this work includes some digging into the readily available literature on the Net.

A couple of months ago I run into an excellent summary on  Nezara viridula from University of Florida (UF). 

Figure 11 of the UF article shows a picture of the feather-legged fly (Trichopoda pennipes) that is similar to the following picture that I found in a Wikipedia article on this fly:

Feather-legged Fly (Trichopoda pennipes) 2.jpg

More importantly, Figure 12 of the UF article shows a picture of an adult Nezara viridula too, with four parasitoid eggs on its back. That picture made me remember that I took a similar picture myself last year. (See the second picture on this page.) You can also compare my picture with the following one that I have borrowed from the Wikipedia article:

I think I have every reason to believe that I found an indirect evidence of the presence of Trichopoda pennipes in Hungary. Its presence is not really surprising either. Why? Because feather-legged fly has been present in Europe for some years according to these references:

The arrival of this fly in Hungary (or the alternative explanation mentioned in the introduction) hopefully means that the Nezara viridula population will gradually drop to a tolerable level in our country.


The UF article: http://entnemdept.ufl.edu/creatures/veg/bean/southern_green_stink_bug.htm
The Wikipedia article: https://en.wikipedia.org/wiki/Trichopoda_pennipes
Info on tachinids in French: http://aramel.free.fr/INSECTES15-53.shtml

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