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Big Fat Water Bug - Benacus griseus

Big Fat Water Bug - Benacus griseus
Harrison County, Mississippi, USA
Size: Aprox. 2.5"
Fall 2005. This Water Bug seemed to think that no one would notice him swiming around in a swimming pool.... as if he would just blend in.. LOL. I don't know what it is, but it was big.

image lightened
to show detail of eyes and allow better comparison of L. griseus with images of L. americanus such as this one

schming- Aquatic insects a

Aquatic insects are generally measured from the front on the head to the end of the abdomen. That would make yours approximately 2 inches, or 50 millimeters, or 5 centimeters.

Can you clarify the location? Mississippi doesn't have a Harris County.


Stephen Cresswell
Buckhannon, WV

Harris Co, MS
Gulfport, MS is the main center of population.

My family is from Mississippi (I was born in Jackson), and I am certain there is no Harris County in the state. If this is from the Biloxi-Gulfport area, then the county is Harrison. But it might be good for the contributor to confirm the location to make sure what was intended.


Stephen Cresswell
Buckhannon, WV

Harris was a typo ~
Oops ...sorry about that. It's Harrison of course. I used to live in Houston, which is Harris Co. and sometimes I get the two mixed up.

The WaterBug was found about 5 miles from the coast, in a semi swampy pine forest area, near the town of Pass Christian and Gulfport.( just south of I-10 at Menge Rd )I dont know why the pic date shows up as 2003, it was taken in the fall of 2005 shortly after Katrina came thru'.

You're right.

Belostoma sp.
Maybe B. flumineum? The color looks quite dark, was it wet when you took the picture? Slater and Baranowsky's How to know the true bugs, says: "...brown in color with darker leg markings...head is rather short, lenght before the eyes being equal to the lenght between the eyes..."

Giant Water Bug was doing laps in the pool : )
so, yes he was still wet when I took the photo...although he was still quite dark nonetheless.

Thanks for the ID help, you guys are swell.

maybe Lethocerus americanus....giant waterbug

I agree
I have collected several of these insects. Your ID is right on.

Giant water bug
Lethocerus sp. are much larger, at least 4 to 6cm long.

I agree with Laura that Lethocerus are generally much larger, but the body form is much more consistent with that genus than with Belostoma. Consensus anyone?:-)

giant water bug
The large bug found in the swimming pool in Harrison County, Mississippi is Lethocerus griseus (Say). It is of about average size for this species, which is common in the southeastern U. S. I have in my collection both larger and smaller specimens, and collected this bug near Biloxi in 1949.
This species can be separated from L. americanus, which is quite uncommon so far south, by the evenly curving anterior margins of the eyes; L. americanus has more bulging eyes. The best key character of griseus is the pad of "fur" rather than grooves on the inner face of the fore femur; griseus is the only Lethocerus species with this feature.
I should have mentioned, Lethocerus are easily distinguished from the closely related genus Belostoma, by the hind tibia and tarsi being flattened and wider than the middle ones, whereas they are about the same width in Belostoma.

Moved to Guide
I created a new guide page for the species and moved this there. I hope you don't mind my quoting your diagnosis of the species on the guide page.

Thanks for your help!

English unit ruler
I believe the insect is 2+ inches long, 5 cm or more--that ruler is in "English" units.

Patrick Coin
Durham, North Carolina

Lethocerus sp.
Now that the measuring units have been clarified (I was having problems with that myself) I think I have to agree with Andy and Eric, because the general shape does look a lot more like Lethocerus than Belostoma.

Interesting measurement terminology, Patrick -
I find it funny to see it described as "English", since the English have generally used the metric system since the eighties (with the notable exceptions of miles and pints), and inches etc. are commonly referred to as the Imperial system in the UK. I guess the US is the new Imperial power. :)

Don't go there. PLEASE.
Great photo btw, i've seen one or two before, but I've never been able to photograph one

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