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On Treehoppers…or…What the Heck is THAT For?!?!

June 26, 2012

One of the great ironies of the insect world: the group of bugs that is arguably the most charismatic, the most bizarre, and the most alien-like on Earth is unknown to most people.  Easily overlooked because of their small size and the fact that they don’t bite or sting people, treehoppers are entomologically famous for their often fantastic and elaborate shapes.  Treehopper species in North America (including North Carolina) tend to be rather sedate in appearance, but many of their tropical counterparts have been described, with good reason, as “mild-mannered minimonsters”.  Some of these things really have to be seen to be believed…

Umbonia crassicornis, a thorn mimic treehopper

Umbonia crassicornis, a thorn mimic treehopper

As with the spittlebugs (the subject of a previous blog post), treehoppers are part of the insect order Hemiptera, characterized by having their mouthparts evolved into a permanent ‘straw’…an adaptation for sucking up liquid food.  And like those crazy spittlebugs, treehoppers are exclusively vegetarian, eating only plant sap (although these critters eat phloem sap, rather than the xylem diet of spittlebugs).

Cladonota sp., a treehopper that mimics a piece of plant

Cladonota sp….a plant mimic?

What marks treehoppers as different from other insects is the extreme plasticity of one of their body parts.  One of the parts of their exoskeleton…the top part of their thorax just behind the head….is called the pronotum.  Basically, think of this part as their ‘upper back’.  For some unknown reason, this pronotum is amazingly variable across species.  And by ‘amazingly variable’, I mean that this structure looks totally and completely different in insects that are closely related to each other.  In some cases, researchers believe that these extravagant forms have evolved to provide camouflage and protection for the bugs.

For example, species in the treehopper genus Umbonia are convincing thorn mimics whereas species in the genus Cladonota resemble bits of twig and bark.  Species in the genus Heteronotus are über-convincing wasp or ant mimics.  However, the outlandish shapes displayed by some treehopper species defy our attempts at explanation, leaving it up to our imaginations to decipher their adaptive advantage (Bocydium…what the heck is THAT for??)!

Bocydium sp.....a Neotropical treehopper

a species of Bocydium…a helicopter mimic?!?!?

I’ve been fortunate to have chosen treehoppers as one of my research subjects.  I describe their biodiversity and study their biology by reconstructing their family tree….their evolutionary background.  Once we know about the evolutionary history of a group of organisms, we can study (and say something meaningful about) their biology and geographic distribution.  And when the organisms you study are as wacky as treehoppers, this is an exciting science!  You can check out some pictures of treehoppers and related insects on my Flickr photostream at: http://www.flickr.com/photos/jasoncryan/

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7 Comments leave one →
  1. Margaret deGravelle permalink
    July 11, 2013 12:05 am

    Doing a search about treehopper bites, I see there are several links claiming they don’t bite. One reason because of their mouthparts. Please note that at least one species of treehopper bites humans. I don’t have an image or ID handy. It was a very light yellow/white model thriving in a somewhat diverse and watered Seattle home garden. The bite left a very red and periodically itchy long term welt. I compare it to a biting midge (no-see-um) and less so to a dog flea. This bite closely resembles bed bugs in posted insect bite images, but I watched the treehopper bite me and then the wound developed. It was a sharp sting so the brush off was immediate. Potent little bastard!

    • jasoncryan permalink
      July 15, 2013 9:28 am

      Hi Margaret! Thanks for your comment…wow…really interesting! Reports of hopper bites are exceedingly rare, as you can imagine, because of the fact that they are exclusively plant-feeders and their mouthparts are adapted to be essentially a ‘straw’ through which they suck up liquid. Feeding observations have documented that they do probe the substrate with their ‘straws’, so I suspect that this little guy landed on you and probed you to see if you were an edible shrub! Very, very unusual, but not totally unheard of…Thanks for sharing!

  2. shanterria hampton permalink
    February 3, 2014 11:14 am

    i dont really understand these bugs,but the pink ones are soooooo cute!!!!!!!!!!!!

  3. September 11, 2017 7:35 am

    A former student of mine said that the oak tree hoppers are dropping liquid onto her outdoor chair. I hypothesize with something similar to honeydew? Do you know anything about their exudate? Thanks. Fankhadb@ UC.edu.

    • jasoncryan permalink
      September 11, 2017 12:47 pm

      Hi David! Thanks for your question. Yes, indeed, treehoppers (like all of their relatives in the hemipteran suborder Auchenorrhyncha, including leafhoppers, spittlebugs, cicadas, and planthoppers) are phytophagous (plant-eating) insects. Treehoppers specifically ingest phloem sap from their host plants, and process quite an abundance of that liquid through their alimentary systems in order to meet their nutritional needs. The excess liquid is excreted in a ‘concentrated’ form….the ‘honeydew’ you referred to. I don’t know the exact chemistry, but I understand that the sugar content of honeydew is relatively high, and thus makes a desirable food source for other animals (primarily ants, in the case of treehoppers; there are many fascinating instances of symbiotic associations between the hoppers and various ant species). And yes, the honeydew excreted by treehoppers certainly can be abundant enough to drip onto whatever is around the hopper aggregation, and because of the sugary content often results in mold growth.

      Hope that helps!

      Best,

      Jason

Trackbacks

  1. A Greater Appreciation For: Paleontology | Research & Collections
  2. On Planthoppers…or…Some of the Coolest Bugs EVER! | Research & Collections

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