Currently viewing the category: "Horntails, Wood Wasps and Sawflies"
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Subject: Orange Abdomen – Plant eggs in stems?
Location: Mira, Venice, Italy
May 17, 2015 12:26 am
Hi dear Bugman,
On these roses these insects, I counted 4, proceeds undisturbed to crack the stems, leaving behind a kind of scar. I could go as fat as touching them. The have this very bright orange abdomen and very dark rest of the body and wings. The length is about 1-1.2cm. Apparently the upload does not work. I posted two pics:
I’m really curios about this. Glad to find a service like this online. Hope it works :)
Signature: Lord of the manor

Rose Sawflies

Large Rose Sawflies

Dear Mauro, Lord of the Manor,
These are Sawflies, nonstinging relatives of Bees and Wasps whose larvae feed on plants, sometimes eating the leaves, and sometimes feeding on other portions of the host species.  We quickly identified your Sawflies as Large Rose Sawflies,
Arge pagana, on the Dutch site where it states:  “The Large Rose Sawfly saws a hole in a Rose (plant) and lays eggs.  The larvae eat the rose. But usually there is not much damage,  because the larva has many natural enemies.”  On Nature Spot it states:  ” Like all sawflies, female Large Rose Sawflies are in possession of a little saw. With it they make parallel cuts in the fresh shoots of the host plant. In the cut a bunch of eggs is deposited. The larvae hatch quite quickly and move in a group to the freshly emerged leaves. The young larvae (yellow with black spots) stay together for quite some time, capable of eating the entire shoot. Older larvae lead a more single life and eat from older leaves as well.”   We also located an Italian site, that might have helpful information for you. 

Thanks Daniel for the quick and comprehensive answer! I took pictures of the larvae last year without knowing they were Sawflies.
Thanks also for the great service you are providing!

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Subject: what is this?
Location: Southern Illinois
March 28, 2015 6:48 pm
Went on a walk through a wooded area in southern Illinois and saw this insect. I’m not quite sure what it is and I’ve looked all over the internet. Picture taken 3/28/15.
Signature: Megan

Resembles Black and Red Horntail

Parasitic Wood Wasp Resembles Black and Red Horntail

Dear Megan,
Wow, this one has us confused.  It seems to resemble the Black and Red Horntail,
Urocerus cressoni, but there are too many inconsistencies for us to be sure.  The Black and Red Horntail is described on BugGuide as being:  “head, thorax and wings black, abdomen red (amount of red variable), two pale spots behind the eyes, antennae black with white tips.”  Additionally, the black and white legs are evident in images on BugGuide.  We cannot make out the “pale spots behind the eyes” in your image, and it also appears that the antennae are tipped in black.  There is no obvious ovipositor, so it could be a male of the species, however, March is many months earlier than all the sightings documented on BugGuide.  With all that said, we do not believe this is a Black and Red Horntail, but we cannot provide any other possibility at this time.  We are posting your image and we hope to get some input from our readership.

Eric Eaton Responds
This is a tough one.  Near as I can tell, though, it is a parasitic wood wasp in the family Orussidae:
They are common, but not seen very often.  They are related to sawflies, but instead of being vegetarians in the larval stage, they are parasites of wood-boring insects, especially beetles.  This one might be ovipositing.
The curly antennae are the best clue here, but the angle is awkward and I’d like to see other images, if there are any, before offering a definitive ID.  I’ll stand by Orussus sp. for now, though.
author, Kaufman Field Guide to Insects of North America

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Subject: On our burr oak, in Texas.
Location: Arlington, TX
March 27, 2015 10:49 pm
My partner asked me to grab a picture of this and see if I could help him identify it. He’s been seeing these on our burr oak, here in North Texas, since the leaves started budding this week. He’s says there are “lots” of them. He seems to think they have been laying eggs, but I haven’t seen what they have been up to to confirm this impression (and, obviously, he’s not really a Bug Guy).
For the record, it is late March, and the weather has been warming up here for a couple of weeks. (it’s up to the 70’s and low 80’s this coming week, already.)
I have included both the closer detail crop, adjusted for clarity, and the wider shot for some idea of size. They are small, probably… a half-inch? Maybe? Those are very early leaf buds at the end of an almost twig-like branch that this one is sitting on. (Sorry it is not more clear, it was already evening when he asked me to take the photo.)
Thanks! I hope you can help us out!
Signature: Kelly in Texas

Sawfly, we believe


Dear Kelly,
We believe this is a Sawfly, a non-stinging relative of wasps and bees.  The theory that it might be laying eggs is valid.  The larvae of Sawflies are often confused for caterpillars, and if they are numerous, they can defoliate some plants.  We are going to continue to research this request and we are also going to try to get an opinion from Eric Eaton.
  The Ladybird Johnson Wildflower Center website mentions “oak leafmining sawfly (Profenusa lucifex)” as an insect that feeds on Burr Oak, and though we could not find the species pictured on BugGuide, members of the genus look similar.

Eric Eaton confirms Sawfly and provides possible species identification
Yes, definitely a sawfly, perhaps Pristiphora chlorea.
Do you know how to do an “advanced search” in Bugguide?  That is often how I come up with answers for you.  Don’t get me wrong, I enjoy the challenge of finding you an answer! :-)

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Subject: What is this insect that stung my daughter?
Location: SE Michigan
January 2, 2015 8:59 pm
I have never seen an insect like this before. I assume it is some kind of bee, although the shape is all wrong. It stung my daughter’s hand back in September and she had a horrible reaction for several days. She ended up being given an epi-pen for future stings. It was hanging around our back deck; we live in southeast Michigan, a little north of Detroit. I tried searching on google, both for websites and doing an image search, to no avail. I’d love if you could help identify it!
Signature: Sharon in Michigan

Pigeon Horntail

Pigeon Horntail

Dear Sharon,
We are very interested in your report.  This is a Pigeon Horntail, a species of Wood Wasp.  We generally advise our readership that though they appear to possess a stinger, they are harmless as the stinger is actually an ovipositor used to lay eggs.  When in the act of oviposition, the female Pigeon Horntail inserts her ovipositor into wood to lay the egg beneath the surface.  Since it can penetrate wood, it would seem to indicate that the ovipositor might also penetrate human skin, though we believe incidents like that are extremely rare.

Wow, thank you so much for this information, it’s quite fascinating.  Clearly she must have been stung by something else – in fact, in further questioning my kids, they clarified that they had never said that was the insect that did so, just that it was around at the same time and they thought it was interesting-looking and unfamiliar.  Wish I knew what HAD gotten her, but oh well!
Thanks again for your prompt response!

Thanks for that update Sharon.  We will continue to advise our readers that Pigeon Horntails are harmless.

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Subject: Identifying
Location: Edmonds, WA
December 13, 2014 12:19 pm
Dearest Bugman,
I have lived in western Washington for 43 years. I have never seen this bug before. It was caught in a spiderweb and already dead. I have kept it in a plastic container since late summer DYING to know what it is. Can you help please?
Thanks so much,
Signature: Catherine

Wood Wasp

Wood Wasp

Dear Catherine,
This impressive female Wood Wasp or Horntail might be
Urocerus albicornis, which you can find pictured on BugGuide.  Though the antennae are missing, and we cannot say for certain that your individual had white antennae while living, and though the white “cheeks” are not apparent in your image, the distinctively striped legs are nicely illustrated, and that feature helped us to narrow the identification possibilities.

Wood Wasp

Wood Wasp

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Subject: Caterpillar swarm in Costa Rica
Location: Costa Rica higher elevation
October 31, 2014 9:12 am
These caterpillars(?) appear seasonally in the higher elevations in Costa Rica. (1500m/5000′ MSL). They are 3-4″ long and appear to burrow as a group in the ground (in our yard and surrounding farmlands).
We don’t know what they are (or whether they are a problem?) but they have a marvelous locomotion. They crawl on top of each other for awhile, then they all pause as if catching their breath, then resume. This video was taken on the road outside our house.
What are they and do they benefit or damage the plants and animals?
Signature: Bugged in Costa Rica

Sawfly Larva

Sawfly Larva

Dear Bugged in Costa Rica,
We do not believe these are Caterpillars.  We believe they are Sawfly Larvae, relatives of wasps and bees.  There are Australian Sawfly Larvae known as Spitfires that look similar.

Aggregation of Sawfly Larvae

Aggregation of Sawfly Larvae

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