Stag and “stagette” beetle

Lucanus capreolus, female (L) and male (R) | Fort Defiance Park, Illinois

Lucanus capreolus, female (L) and male (R) | Fort Defiance Park, Illinois

Last month I posted some photos of the very “stag beetle-ish” looking longhorned beetle, Parandra polita. Chestnut brown in color with large, forward projecting mandibles, this member of the longhorned beetle subfamily Parandrinae looks almost nothing like longhorned beetles in other subfamilies but very much like a small species of stag beetle (family Lucanidae). If it weren’t for the straight rather than elbowed antennae, even experienced coleopterists might be fooled by its appearance. The beetle had been attracted to an ultraviolet light setup in wet bottomland forest at the southern tip of Illinois where the Mississippi and Ohio Rivers meet. Perhaps not coincidentally, several true stag beetles representing both males and females of the species Lucanus capreolus were attracted to the lights that night as well.

Males are distinctive by their large, sickle-shaped mandibles.

Males are distinctive by their large, sickle-shaped mandibles.

The genus Lucanus contains the largest stag beetles in North America—the most desirable of the handful of species it contains being L. elaphus (North America’s largest stag beetle) due to the male’s outrageously enlarged mandibles and the species’ general scarcity. Lucanus capreolus nearly matches L. elaphus in size and has an equally broad distribution across eastern North America, but it seems to be a more common species and has the male mandibles only moderately (though still distinctly) larger than the female. Despite its more routine occurrence, I rarely see more than a few individuals at a time, and they are almost always all males. This night, however, I was fortunate to encounter not only males but several females as well. I’ve previously photographed the female of this species (Diminishing Stag Beetle), but this was my first chance to photograph both male and female together.

Females have much smaller mandibles (but are still capable of delivering a painful 'nip').

Females have much smaller mandibles (but are still capable of delivering a painful ‘nip’).

While male L. elaphus are undeniably distinct, I frequently see confusion about how to distinguish male L. capreolus from L. placidus (the third eastern North American species of the genus, occurring more sporadically than L. capreolus), and separating females of all three species can be even more confusing. Male L. elaphus are readily identified by their greatly elongated and multi-toothed mandibles, but a suite of characters may need to be employed for females and non-elaphus males. The best character to use for L. capreolus are the distinctly bicolored femora that are yellowish at the base; however, color can be variable and some individuals will exhibit the more uniform chestnut-brown color typical of L. elaphusLucanus placidus, on the other hand, is usually distinctly darker in color than either of the other two species. Surface sculpture of the elytra and pronotum also offer useful characters. The elytra of L. capreolus and L. elaphus are rather smooth, while in L. placidus they are more distinctly punctate/rugose. The pronotum of both L. capreolus and L. placidus, however, is usually distinctly punctate compared to the relatively smooth pronotum of L. elaphus. The shape of the labrum (projection between the mandibles) is also usually distinctive and is not influenced by gender like the mandibles. In L. elaphus the labrum is rather pointed, while in L. capreolus and L. placidus it is more blunt (indeed, in L. placidus the labrum can almost be described as quadrate, or “squared”). Lastly, the number of teeth on the inner margin of the mandibles is usually diagnostic for females of the three species—L. capreolus possessing one tooth, L. placidus possessing two, and L. elaphus possessing more than two.

Unlike in most insect groups, males rather than females.

Unlike most insect groups, male stag beetles rather than females are generally larger.

© Ted C. MacRae 2014

Diminishing Stag Beetle

This past June I made a couple of trips to north-central Arkansas. They were my first real efforts to collect insects in Arkansas, despite hundreds (literally) of trips to various localities throughout the Ozark Highlands in adjacent southern Missouri. The similarities between the two areas were obvious, yet there was also the feeling of a brand new area just waiting for exploration. On the second trip, I found a campground that looked good for blacklighting to see what wood-boring beetles I might be able to attract amongst the surrounding pine/oak-hickory forest. The evening was warm (very warm!) and humid with no moon—typically ideal for blacklighting, but beetles were sparse at the sheets for some reason (perhaps deterred by the obnoxiously unrelenting yells of drunk Arkansans and their out-of-control offspring?!). The evening, however, was not a total loss—at one point an enormous stag beetle landed on the top of the sheet.  It was so big that I couldn’t even fit it into the viewfinder of my camera:

I fiddled with the camera and changed some settings.  I got a little more of the beetle in the viewfinder this time, but it was still just too big:

Additional fiddling with the camera allowed even more of the beetle to be seen:

As I took the photographs, I even began wondering if the beetle itself was actually shrinking:

Eventually, it turned out to be a normal-sized beetle after all:

This is a female of the common eastern North American species Lucanus capreolus.¹  I don’t seem to encounter female stag beetles as often as the males, so this was still a nice find on an otherwise frustrating night.

¹ Two bonus point in the current BitB Challenge session to the first person who correctly explains how I know this.  Overall contenders: here’s your chance to score an advantage as we enter the final stretch in the current Challenge session.

Copyright © Ted C. MacRae 2011

North America’s largest stag beetle

 

Here is the full-sized photo that provided the image for yesterday’s Super Crop Challenge #3.  The insect in the photo is, of course, a fine example of a male Lucanus elaphus – the giant stag beetle (family Lucanidae).  This striking insect is easily among North America’s most distinctive and recognizable species by virtue of the enormously super-sized mandibles sported by the males.  Its fearsome appearance belies the true nature of this harmless beetle, which spends its days feeding on sap that flows from wounds on the trunks and roots of trees.  Males use their massive mandibles in combat with other males, not for “biting,” but rather as tools to pry and lift their adversaries before dropping them to the ground.  Some marvelous photos of this behavior in a related European species can be seen at Stag Beetles Lucanus cervus Mating Behaviour.

I collected this specimen many years ago at an ultraviolet light (“blacklight”) that I had setup in the pine/oak forests at Pinewoods Lake, Carter Co., in the southeastern Ozarks – one of my favorite 1980’s beetle collecting spots.  This was in my early days of studying beetles, during which time I was actively collecting material as part of my statewide surveys for the families Buprestidae (MacRae 1991) and Cerambycidae (MacRae 1994).  Lucanus elaphus is not a commonly encountered species, especially in the western reaches of its distribution here in Missouri, and I’ll never forget my rabid excitement when I encountered this fine major male at my blacklight sheet.  For many years afterward it remained the only individual that I had ever encountered, until a few years ago when I came across a group of two males and one female feeding on a sap flow in a wet bottomland forest along the Mississippi River in the lowlands of southeastern Missouri.  I encountered another male the following year at a nearby location “rafting” on debris in floodwaters from the nearby river, and two weeks later at that same site I picked up several males and females in a fermenting bait trap.¹  Like most “uncommon” species with broad distribution across the eastern U.S., I suspect that its apparent rarity is an artifact due to habits that make it infrequently encountered rather than being truely scarce.

¹ I have used fermenting bait traps to collect a wide variety of beetles, but especially longhorned beetles.  My recipe is based on that described by Champlain and Knull (1932) – bring 12 oz. dark molasses and 12 oz. beer up to 1 gal. with water, mix well and add a packet of dry baker’s yeast to get the fermentation started.  Hang a 1/2-gallon milk jug with big holes cut in the sides in a tree along the edge of a woods and add ~1 quart of fresh liquid.  It generally takes 2-3 days for the liquid to really start fermenting and become attractive, and it will remain so for about another week or so.  Check traps every 2-3 days by pouring the liquid through a kitchen strainer into another container – reuse or replace as necesssary. Place the collected specimens in vials of water to wash off the molasses residues, and either pin immediately afterward or transfer to 70% ethanol for longer term storage.  Some of the more desireable species I’ve collected in this manner, besides L. elaphus, are Plinthocoelium suaveolens, Purpuricenus axillaris, P. humeralis, P. paraxillaris, Stenocorus cylindricollis, S. shaumii, Sarosesthes fulminans, Stenelytrana emarginata [= Leptura emarginata], and S. gigas [= Leptura gigas].


Congratulations to Ben Coulter and Janet Creamer, both of whom correctly identified the species and most of the mouthparts.  Each earned 14 pts and, thus, tied for the win, while JasonC. earned 5 pts. to take the final podium spot.  The pointed structure is the labrum (its shape distinguishing it from other North American species of the genus), and it is flanked on each side by the fuzzy yellow galeae (derived from the maxillae) and the labial palps.  Nobody correctly named the galeae, which seem to be greatly elongated and hairy in stag beetles as a function of their sap feeding behavior.  A portion of the left maxillary palpus can also be seen in the corner of the photograph, but nobody scored those points either.  Brady Richards just missed the podium, but his witty reference to Gene Shalit (if not immediately picked up on by me) earns him an honorable mention.

With points being formally awarded now beginning with the previous competition (ID Challenge #1), I’ll start keeping an overall leaders board, and with wins in both competitions Ben takes a commanding lead in the overalls with 23 pts, followed by Janet Creamer at 14 pts and TGIQ at 8 pts.  I guess I should start thinking of some sort of tangible prize for winners periodically – suggestions welcome.  Stay tuned for another issue of Super Crop Challenge or ID Challenge in the near future.

REFERENCES:

Champlain, A. B. and J. N. Knull.  1932. Fermenting bait traps for trapping Elateridae and Cerambycidae (Coleop.).  Entomological News 43(10):253–257.

MacRae, T. C. 1991. The Buprestidae (Coleoptera) of Missouri.  Insecta Mundi 5(2):101–126.

MacRae, T. C. 1994. Annotated checklist of the longhorned beetles (Coleoptera: Cerambycidae and Disteniidae) known to occur in Missouri. Insecta Mundi 7(4) (1993):223–252.

Copyright © Ted C. MacRae 2010