Stange black insect
Location:  Costa Rica
September 21, 2010 11:05 pm
I hope you guys can help me!
Recently I went on a trip in February to Costa Rica for two weeks. I took many bugs pictures and this is the only I cannot identify.The pictures were taken by a large river. The insect was about one inch long, maybe a little less. It had wings which it flew with. The back end of it, it was able to move much like a scorpions tail, which is the part I found most fascinating… Its pincers were also quite large for its size.
No guide I asked knew what it was, all assumed it was a scorpion till I told them it flew.
Any help would be much appreciated! 🙂
Signature:  Christine Claes

Transvestite Rove Beetle

Hi Christine,
This is some species of Rove Beetle in the family Staphylinidae, though we are not certain if we will be able to determine an exact species for you.  According to BugGuide: “Thin, active beetles with shortened elytra that do not, at first glance, resemble beetles. In typical form, body appears to be divided into four parts when viewed from above. Family characteristics:
body shape typically elongated, with parallel sides
elytra short (about same length as pronotum, or only slightly longer; wings are functional in most), typically exposing 3-6 (usually 5-6) abdominal segments, though abdomen concealed in a few
coloration usually dark but some brightly colored
antennae thread-like or clubbed
tarsal formula variable, usually 5-5-5 (sometimes 4-5-5, 5-4-4, etc.)
Some species run with abdomen curled up over thorax as if it were a stinger but no rove beetle has a stinger.

Transvestite Rove Beetle

Identification of Transvestite Rove Beetle Courtesy of R. Randy Hoffman
Today’s “Strange black insect” is (I kid you not!) the “Transvestite Rove Beetle”
September 22, 2010 6:42 pm
Cue Tim Curry to put on the fishnet and grab the microphone, Daniel! After scouring through lots of Google images for “Staphylinidae” + “Costa Rica” for the rove beetle posted as today’s “Strange black insect”, I get an excellent match at This has to be a specimen of <i>Leistotrophus versicolor</i>, the Transvestite Rove Beetle. The blog post has a fascinating discussion of how some males of the species imitate females. “Don’t get strung out by the way that I look,
Don’t judge a book by its cover.” 🙂
Signature: W. Randy Hoffman

Transvestite Rove Beetle

Dear W. Randy Hoffman,
Thank you first for tracking down this identification, and perhaps even more for the brilliant pop culture citation.  We really don’t want to give too much away regarding the content of Daniel’s book, but there is a section on male Cockroaches that imitate females to gain the upper hand on dominant males.  It is a chilling account that includes dismemberment.  The link you provided is a great place to start, and it includes this information:  “Males of this rove beetle are divided into two types, normal butch specimens and small, effeminate ones. The small, effeminate males can find honey-pots, but they have little hope of defending them against the bigger males, so their chances of building a harem are next to nothing. These males have evolved another means of making sure they pass their genes onto the next generation. They sneak past the normal males using their effeminate appearance as a disguise and under the harem owner’s nose they have it away with the females he has been so carefully guarding. This strategy is almost flawless, but now and again the transvestite male is caught prancing around in the harem by the owner male and the only way he can avoid being torn limb from limb is by assuring the aggressor of his femininity and giving in to a ‘mating’.  One sore behind later, the transvestite male carries on sneakily copulating with the females in the harem, only slightly more nervous for his unpleasant experience.
” We also wanted to research this Transvestite Rove Beetle, Leistotrophus versicolor, a bit further.  We have verified the information you provided us by locating another website from Colorado State department of Entomology that has a 1995 paper by Robin Corcoran posted online entitled Intraspecific Sexual Mimicry in Insects.  That paper contains this information:  “MIMICRY TO GAIN ACCESS TO MATES  Large males of the tropical rove beetle, Leistotrophus versicolor, establish territories on bonanza resources, vertebrate dung and carrion (Forsyth and Alcock 1990).  Females attempting to feed on flies attracted to these sites are courted and usually mate with the territorial males.  Some males in this species have adopted an alternative strategy.  These males are considerably smaller, have smaller and differently shaped mandibles, and effectively mimic females.  This enables them to gain access to larger male’s territories, soliciting courtship from the territorial male and even mating with females while being courted by the resident male.  Resource defense polygyny enables large males the opportunity to monopolize mates.  This strategy has led to the evolution of alternative male reproductive tactics in which small males can successfully deceive larger males by mimicking females.  Small males, however, also exhibit behavioral flexibility, mimicking females only in the presence of larger males but attacking and driving off smaller rivals.”   Again, thanks for this wonderful addition to our website.

Glad you liked my ID text; also glad you were able to verify the information. One other point mentioned in the blog post that I found fascinating was that these beetles exude a rotten-smelling chemical from the pygidial glands in their abdomen, use their heinie to rub the stuff on a leaf, and wait to snack on the flies that it attracts. “I see you shiver in antici…pation!”

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