Entomology (Study of Bugs)/laelius pedatus


QUESTION: A friend of mine in Seattle was stung badly by these wasps.  She developed huge welts and is still itching days later.  

I was horrified.  She'd been gardening and I do some myself.  I've tried to find out more about them but can find little on the web.

I would like to know where they tend to live, where they come from, are they invasive, why aren't gardeners being warned more about them?  Basically, I want to know more - to protect myself and other gardening friends.  What I did find on-line suggests that not everyone reacts so badly to the stings - is it known why?  Is there any way to know whether one is likely to react strongly (my friend who was stung is NOT allergic to bees) and how to avoid them, what to watch for?  If there is any individual who specializes in studying them, would it be possible to communicate with him/her?

Thank you for any response and/or links to more information you can provide.  

Thank you

ANSWER: Dear Cathleen - How were these wasps identified? The species Laelius pedatus (Hymenoptera: Bethylidae) is a very tiny (~1/10") wasp that is parasitic on grain-infesting beetles in the family Dermestidae, and thus very unlikely to be encountered in a garden situation; there would be absolutely no reason that I can think of why any warning would be necessary. Also, I can find no record of them ever having been reported as stinging humans. I have come across references to an article in Italian stating that a related species, Laelius anthrenivorus (also a parasite on dermestid beetles) had "attacked" humans, but no details were available. The only record of any Bethylid wasp stinging a human I can find occurred in New Zealand as was reported as "A small white lump c. 3 mm in diameter and 1 mm high came up and it stung for about 5 minutes."  Bethylids often tackle prey much larger than themselves, and thus have evolved venom designed to immobilize arthropod prey quickly. This is in contrast to social wasps such as yellowjackets, hornets, etc. that have evolved venom designed to inflict maximum pain on vertebrates, a very useful (to the wasps) when defending their nests.
  All that aside, it is very common to find many varieties of wasps in gardens, as other insects there, particularly caterpillars, are an attractive food source for them. I have an 8000 sq. ft. vegetable garden where I see wasps 'patrolling' there every day, and I have yet to experience a sting from any of them. As long as you avoid bothering them, they will leave you alone. Also, different individuals can vary greatly in their response to arthropod venoms in general - what causes a minor annoyance to you might be a major medical issue to a hypersensitive person.

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QUESTION: Thank you for responding

My friend found a report of exactly the same sting reaction on bugguide.net   (http://bugguide.net/node/view/41130).  This is one of the first items that comes up when you Google laelius pedatus.  Someone reported exactly the kind of sting she got.  And there was some discussion about identification.

They were tiny things which appear to have nested in a fern bed at my friends house.  They didn't look like yellow jackets or other usual wasps, so she didn't know she was "bothering" them.  She was just clipping dead fern fronds.

I understand that getting stung or having such a strong reaction may be rare.  But it still astounds me that the multiple gardening sources I've read never even mention such a possibility.  I would have been MUCH more careful to look at tiny flying insects if I'd known.  If such a strong reaction is possibly an allergic response, it is even more important that that information be widespread.

I will investigate the L. anthrenivorus you mentioned.

Thank you again for taking the time to answer.

Dear Cathleen - Unless the wasps your friend encountered were identified by an authority on that group, I have very strong doubts that they were Laelius pedatus, as their host species simply would not be found in a garden situation. I'm sure that you are aware that there are a myriad of other small wasp species that can superficially resemble this species, and that can be reliably identified only by microscopic examination.
 I do not believe that any 'warning' specific to these insects is at all warranted. From what I have read on the subject of venom hypersensitivity, I would rate the risk of a severe reaction to the stings of wasps such as Laelius to be so low as to approach zero. Almost any time you go outdoors, there will be some chance that you may encounter stinging/biting insects; you just need to be aware of any potentially dangerous ones native to your area. And it is just common sense that if you feel any systemic effects (as opposed to the usual local reaction of a small itchy wheal and sharp pain) after a bite or sting to seek medical attention. You might find the following publications of interest: http://tinyurl.com/mwfy45p, http://tinyurl.com/les84sy, and http://tinyurl.com/keq3f3n
  There are publications in most, if not all, states on their hazardous fauna, published by state universities and usually available through county Cooperative Extension Service offices. See http://tinyurl.com/kyafvxr, http://tinyurl.com/mcl84s9, http://tinyurl.com/n7m4t5e, and http://tinyurl.com/l8a5o4x for some examples.

Entomology (Study of Bugs)

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Ed Saugstad


Will accept most questions in general entomology, including those related to medical entomology, taxonomy, ecology, arthropod surveillance, and pest management. If you are requesting a 'mystery bug' identification, PLEASE either attach an image to your question, or post an image on a web page (such as Flickr) so that I can look at it, as verbal descriptions frequently are insufficient for a definitive identification.


21 years in the U.S. Army as a medical entomologist; duties varied from surveillance of pest populations (including mosquitoes, cockroaches, ticks, and stored products pests) to conducting research on mosquito-virus ecological relationships and mosquito faunal studies. Ten years as a civilian analyst for the Department of Defense, primarily on distribution of vector-borne diseases worldwide. Limited experience on surveillance of agricultural insects in North Dakota and Indiana.

Entomological Society of America, West Virginia Entomological Society, Society for Vector Ecology, National Speleological Society, West Virginia Association for Cave Studies.

American Journal of Public Health, Contributions of the American Entomological Institute, Japanese Journal of Sanitary Zoology, Journal of Economic Entomology, Mosquito News, and Mosquito Systematics.

B.S. in entomology from North Dakota State University in 1963, M.S. in entomology from Purdue University in 1967.

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