Q:  I was wondering are there any other female animals that eat their mate?  And, if you don't mind, what are their names?  My teacher asked us to find out if there are any besides spiders. (Lola, Greenville, Texas)

A silk spider prepares to dine on a smaller silk spider. Photo courtesy of Kumon of Wikipedia.

A:  Few animals in the wild go in for eating mates.  In addition to all orders of spiders, I came up with these that do: scorpions, sagebrush crickets, praying mantises, some shrimp-like creatures (amphipods) and perhaps a type of sea slug (Gymnodoris citrina).  Apparently 30 different animal species, including all orders of spiders and scorpions, eat mates now and then.

"In many species of spiders eating of males is a regular part of the mating procedure, for example in the Australian redback, the wasp spider or in some species of Nephila.  There are, however, related species that are not cannibalistic," emails biologist Jutta M. Schneider, professor at the University of Hamburg. 

"Females in those cannibalistic species with tiny males don’t seem to benefit nutritionally from the extra meal. It is not clear what the advantages of cannibalism for the females could be but we are working on it." 

She and her team investigated wasp spiders, to determine what advantage they could get, and couldn't find much.  Although the females ate 80 % of the males while mating, the investigators found that "consumption of male bodies did not result in any detectable fitness benefit for the female:  neither the number of clutches, nor clutch size or hatching success was affected by consumption of males."

"Males however, do benefit from cannibalism in some species but not in others. There is recent literature about these issues from my lab and the Andrade-lab at Toronto. Self-sacrifice of males may increase their share in paternity and help them to monopolize a female."

Also, some bug-like creatures are just plain vicious.  Scorpions, for example, kill whatever moves (birds, reptiles, mammals but mostly insects and spiders), which makes mating risky for the usually smaller male.

By the way, black widow spider females of most species the world over don't usually eat males.  In two USA species (one is the only species west of Kansas) mate eating has "never been observed in the wild!"  So says the Burke Museum of the University of Washington, busting another myth.

Finally, the New Zealand paddle crab turns the tables; males sometimes eat females while mating.

Further Reading:

Which animals mate for life?  WonderQuest

Fitness consequences of sexual cannibalism in female Argiope bruennichi by Lutz From hage, Gabriele Uhl and Jutta M. Schneider, Institute of Evolutionary Biology and Ecology Journal

Cannibalism in Gymnodoris citrina by Scott Johnson, Sea Slug Forum

Sexual cannibalism and sperm competition in the golden orb-web spider: female and male perspectives by Jutta M. Schneider and Mark A. Elgar, Oecologia Journal, 2004

Avoidance of post-coital cannibalism in the brachyurid paddle crab Ovalipes catharus by Malcolm Haddon, Oecologia Journal, 2004

Spider myths, Burke Museum

Q:  I receive a lot of two dollar bills at the bank with red stars stamped on them. Is this a symbol for something? (Yvonne, Champaign, Illinois)

A:  When you say red stars "stamped" on them, I think you mean stamped (like with a rubber stamp) and not printed by the US Bureau of Engraving and Printing.  But I did ask BEP if they print any stars on paper money.

"The BEP does not stamp red stars on any of its notes," emails Jim Marshall of the Bureau. But it does print stars on bills that it uses to replace notes with printing errors (spoilage), such as, the US seal being printed on the wrong side of the bill. 

"In the early series of our small size notes, the spoilage percentage has been accurately estimated at less than 1% of total notes," emails Ahmet Sandikci of Arcade Currency Palace, Inc. from Tarpon Springs, Florida.

The BEP discards the imperfect note, and replaces it with a good note.  The replacement note is called a star note, because it has its own unique serial number, followed by a star (*) in place of the usual suffix letter (for example:  C01666686 *). 

When the BEP still printed United States Notes (from about 1862 to 1971), they printed a red seal on the bill and red serial numbers, instead of the green seal and green serial numbers presently used on the Federal Reserve Notes.  Any star notes for those bills would have red stars in front of the serial number, and the star looks like a real star, not an asterisk.  See figure.  If you did, indeed, mean printed instead of stamped, this could be the reason why your $2 bills have red stars printed on them (except you would not be getting a "lot" of them).  They are star notes, replacing defective $2 bills.

A 1928 rare $2 star note, a United States Note.  Photo courtesy of Ahmet Sandikci aka Porscheahmet, owner of the Arcade Currency Palace, copyright, used with permission.

As far as a stamped red star goes, marking bills defaces them.  But sometimes people do mark bills to track how money circulates.  The story goes that somewhere along our east coast, sailors on shore leave and looking for a good time customarily invaded a small town.  Locals fed up with their rowdiness complained to the Navy.  So the Navy paid its sailors in two dollar bills the next month.  When the bills flooded the town, storekeepers had a change of heart.

Perhaps someone in your town is stamping red stars on the bills just to find out how they circulate.

In fact, there's a site devoted to tracking money.  It's called 'Where's George?'

Further Reading:

A short history of star notes, Arcade Currency Palace, Inc.

Star notes, Wikipedia

Arcade Currency Palace

Ron's Paper Money FAQ, Ron Pfiester

Where's George?, wheresgeorge.com

Frequently asked questions, Bureau of Engraving and Printing

(Answered Dec. 26, 2006)