Israel Insect World

In independent field observations I (and others, as recently described in different web forums) have noticed the existence of a common pattern of hoverflies death. Syrphidae (mainly from a certain species, probably Syritta Sp.) are found dead on various plants. Explanations were given, including poisoning by toxic fungi from the order Entomophtorales (see here: http://flora.huji.ac.il/browse.asp?action=thread&t=1628)

I attach here a few photos showing dead Syrphidae on different plants from different locations, some of which with swollen abdomen between segments, that might suggest toxicological effects, but most without these symptoms. Some other reasons for syrphidae deaths may be found here: https://kb.osu.edu/dspace/bitstream/1811/4114/1/V54N01_045.pdf.

However, even if we assume fungi contamination, it is hard to understand why most of these dead specimens were found tied to the plants. In addition, it seems that these form of death is restricted to the said species of syrphidae. I would appreciate comments by the forum experts.

במהלך סיורים שונים מצאתי רחפנים מסוג Syritta מתים בהמוניהם כשהם קשורים או דבוקים לצמחים שונים. צורת מוות זו בד"כ מוגבלת לסוג הזבוב הזה וייתכן שהיא נגרמת כתוצאה מהרעלה של פטריות מסויימות, כפי שניתן לראות בחלק מהמקרים ע":י התנפחות הבטן והתרחקות לוחיות הבטן אחת מרעותה. ברוב המקרים לא ניתן להבחין בסימנים חיצוניים על הפרטים המתים ואני מעוניין לבחון האם ישנן סיבות אחרות למוות המוני כזה של המין הספציפי.

This one is from Yaar Ilanot (יער אילנות

from Yaar Ilanot (יער אילנות

Still from Yaar Ilanot

יער אילנות

י

From Zeita Swamp

מביצת זיתא

From Rupin winter pond

משלולית-חורף רופין

Hi Dror,

These are great photos of unknown phenomena for me (I know nothing about about flies).

Anyway I passed the subject to Amnon Freidberg which is the 'the' expert on flies and he replied shortly: "I think it's Melanostoma mellinum, and they probably all died of a fungus".

So that is all I can say in his name. Anyway I'm always glad to learn something new

so thank you very much!

Regards,

Oz

Thanks, Oz.

It turns out this is a well documented occurance and there are many such observations.

I believe the article in the following link is of major importance for this phenomenon. Unfortunately I cannot download the entire paper.

http://www.jstor.org/pss/3758894

I also found this powerpoint presentation on the web:

http://web.yru.ac.th/~dolah/notes/4032605/17%20Zygomycetes%20and%20Trichomycetes%20(1x1).pdf

Still, I am puzzled by the death posture while the flies remain anchored to the plants.

Interesting, I will check if I can get the full article.

Hi dror,

This phenomenon is well known, you can find this research from Israel http://www.springerlink.com/content/78347v2347q75477/

It's a fungus, most probably Entomophthora muscae or close spices which use diptera as a host. It is a sophisticated fungus which first interfere with the fly oxygen flow which force it to climb up to a windy place then it interferes with the nerves which make the fly spread its wings then last start to build spores inside its belly (you can see the swelling belles if you look close). When the spores are ready is just explode spreading the spores from above in a wide range (now when the wings are not in the way) and infest other flies.