Red wasp-like insect that kills spiders
January 23, 2010
I need help identifying the insect in the photo. It was the length of an index finger, bright red with black stripes. It was dragging along a dead (?) furry spider. I need to know if it’s dangerous to humans, it was at the Botanical Garden where I do volunteer work year-round. It’s summer here in Buenos Aires, Argentina, and it’s normal to see more insects (and bigger) than usual, especially in the Botanical Garden (I do volunteer work with cats abandoned in the Garden). The Botanical Garden has a lot of exotic plants found nowhere else in the city. Should I be worried about this bug? I’d appreciate any info you could give me.
Eugenia Pascual
Botanical Gardens, Buenos Aires, Argentina.

Spider Wasp with Prey

Dear Eugenia,
We love your letter and we wish your photograph wasn’t so blurry.  Perhaps your boss will pay for a photography class (shameless self promotion since we teach photography) and then you will better be able to document the wonders of the natural world at the Botanical Gardens.  Please bear with us as we might get a little bit preachy here since we finally connected with the world yesterday and saw Avatar in 3D.  The film profoundly affected us and we thank James Cameron for spreading the word about the need for preservation, the horrors of greed and war and violence, the fragility of our world, the interconnectivity of all things, and the elusiveness of unobtainium.  With that said we will now try to answer your question.  In a most general sense, this is a Spider Wasp in the family Pompilidae, though it will take us some time to try to identify the exact species.  We do not get many letters from Argentina, and we are not sure if there are comprehensive websites devoted to Argentine insects.  The filmic experience of Avatar has made us sensitive, so we might sound harsh when we ask “Did the Spider Wasp try to sting you and drag you back to its burrow to feed its young?”   We suspect your answer will be no, so you have nothing to fear.  The Spider Wasp only wants to provide for her progeny, and she has no desire to sting people.  However, if she is molested, she may sting to defend herself.  Spider Wasps are often very specific about the species of spiders they prey upon.  Adult Spider Wasps feed upon nectar, which is another reason the botanical gardens are an attractive habitat for them.  Based on the coloration and pattern, we suspect your wasp might be in the genus Tachypompilus, which BugGuide indicates is transcontinental for North America.  BugGuide also indicates they prey upon Lycosids, Wolf Spiders, which is consistent with the furry spider description of your letter, though we could never hope to get an identification of the spider from your photo.  Tachypompilus banksi might be the wasp in your photo, and we found a lovely photo posted online on the Insectarium Virtual website.  The site has this information:  “From the observations made known to hunt big spiders Lycosidae, Pisauridae and Sparassidae. The spider is captured by the jaws and dragged by the female. The construction of the nest sites are quite varied: cracks in rocks, hollow logs, cracks in walls or under stones. The nests are accumulations of powdery earth where the female buries the spider digging depressions of about 2 cm deep and only inches apart from one another (multicellular nest, according to Genise). The wasp builds the cell after the spider hunt.
”  Google provides a translation from Spanish.  We are also intrigued with your volunteer job with abandoned cats in the Botanical Gardens.  We can’t help but wonder if the cats are encouraged to hunt rats or if your work involves relocating them.

Thank you for the prompt reply! I apologize for the quality of the picture- I was feeding some cats, leaning over to put down a bowl of Cat Chow, when I turned around and there they were, inches from me face! I dropped the bowl (you can see kibble on the floor in the pic) and ran for it since I am extremely allergic to insect bites and these insects were hands down the biggest I’ve ever seen while volunteering in the Botanical Garden. I borrowed a phone with a camera from a passing tourist, and took the photos as far away as I possibly could, while still shaking a bit. That is why the photo is of such poor quality. I have to say the wasp was minding its own business and never noticed me at all. It was having some trouble dragging the spider up the side of a wall, the spider kept slipping off and falling.
The Botanical Gardens in Buenos Aires, Argentina, were designed and donated by famous Argentine architect Carlos Thays back in the 1800s. Here is the Wikipedia article on it: Sadly, the article is full of innacuracies. Security in the Garden is minimal, so cats are abandoned there on a daily basis. The Park doesn’t contribute any funds towards the care of the cats, which were as many as 300 when the volunteers started their work there. We have managed, through intensive adoption campaigns and castration operatives, to keep the number down to about 100 cats, in spite of the new cats abandoned there every day. The Pasteur Institute does not contribute to their care at all. The Park also suffers from lack of government funding, so maintenance of the grounds and buildings is minimal.
Which brings me back to my original question. I want to avoid disturbing this kind of wasp when I go to the Park to feed the cats, provide basic veterinary for them, and neuter and arrange adoptions. How do I avoid its habitat completely? I know I should avoid cracks in rocks, hollow logs, cracks in walls or under stones. Is there anything else I should know about avoiding this wasp completely? And what about Wolf Spiders? If the wasp had caught one, it means that they live in the Park too. How do I avoid running into them?
Thank you so much for all your help.

Hi Eugenia,
Thanks for all the additional information.  You went through so much trouble to get the photo that we feel badly about commenting on the quality.  Cellular telephones are notoriously poor in the quality of their photos, but they are such a wonderful convenience.  The spider, according to one of the links might also be a Huntsman Spider or a Fishing Spider.  Some tropical Huntsman Spiders are reported to be poisonous, but the bites of Fishing Spiders and Wolf Spiders are not considered dangerous, though all spiders have venom.  The Spider Wasps are not an aggressive group either, and they will not attack you.  Sadly, other than living in a plastic bubble, there is probably no way to avoid them entirely.  Thanks for the clarification on the cats.  We would imagine that 300 cats at the gardens might become quite a nuisance, not to mention that once the rats are caught, they might turn to birds and lizards.  We love cats, but they can upset a natural ecosystem, though the Botanical Gardens are hardly be considered natural.  Have a wonderful day.

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