"Oh look, those spiders are fighting," one of our young visitors said. This didn't seem like a time to talk about birds and bees so I limited my response to an explanation of the difference between Harvestmen (Opiliones) and spiders, discussed in a previous blog.
I thought the harvestman in question was likely the Eastern Harvestman, Leiobunum vittatum, which is a favorite "lab rat" for researchers in the Opilione field. I was surprised when it was identified as a male Leiobunum crassipalpe, the first time it has been reported to Bugguide.
Males and females communicate by sexually specific chemical clues. Then the fun begins. The dance begins with the male trying to get the female in his embrace. The success depends on the size of the males pedipalps according to research published in Behavior. The answer to the age-old question, "Does size matter?" is "Yes" and in Opiliones, the answer is smaller is better! Shorter pedipalps have more mechanical advantage and thus give the male a better grip on a potential mate. On the other hand, larger male size relative to the female will determine how fast mating occurs.
|Mating dance, not a fight - Toronto-Wildlife.com|
Determining the exact species from a photograph is difficult. There are over 130 Leiobunum species and identification depends upon details like sexual organs, mouth parts, etc. The specimen below was posted with the comment "...stocky palps like L. crassipalpe, but the abdomen is long and pointy, like L. vittatum." Experts frequently debate these points, leading to naming and renaming debates. Fortunately for the perpetuation of the species the Leiobunum are able to determine who is who.
|Palps grasping, mandibles at work. Marshal Hedin CC|