A Neotropical Savanna

It’s been a while since my last post. That’s the unofficial blog break. It will be another couple of months until my next one. That’s the official blog break.

This morning as I was checking to see whether the sandpaper plant fruit had ripened, I turned around and met, to my astonishment, this sight:

I thought at first the small tree (in the Fabaceae family, Mimosa subfamily, but not yet identified) had suddenly developed thorns. A closer look, though, showed this collection of insects:

Some quick research at What’s that Bug suggested that this insect is a “thorn treehopper,” possibly Umbonia crassicornis or Umbonia spinosa. After piecing together the information from various sources, I gather that these insects pierce the plant stem to eat sap and also to lay their eggs in the plant tissue. Aggregations are usually of females guarding the eggs of their young. This activity does weaken the branches of the trees, but little other damage is done, according to what I have read so far.

Sorry, Umbonias, after the recent plague of beetles, we were quick on the draw with a pyrethrin-derivative spray. Next time we’ll watch a little longer and see what happens.

In July 2008 John Bennett sent a message to A Neotropical Savanna asking for help in identifying a liana that was in bloom at the time. There ensued a correspondence that made it clear John had some pretty astute observations about Panama nature. I began posting some of his observations as part of my blog, but John is writing about areas that are not really in the savanna, although there is overlap, of course, since we’re both in Panama. I decided it was about time he had his own section of this blog, so you can now bookmark his site and keep track of his writings.

John’s posts are now found in The Panama Naturalist. Browse there and bookmark it or follow his posts with an RSS feed. His current entry is an update on the algarroba tree, which is now budding.

This morning our worker called us out to see what he called la plaga – a plague – of beetles. It was early morning, the beetles were on the back side of the leaf, so I was shooting in the bright, long-shadowed tropical sun hence the poor quality of this and the next image.

Here’s the culprit.

Ted MacRae of Beetles in the Bush says that it is a member of the chafer group (subfamily Melolonthinae) of the scarab beetle family, but he did not have a species name for it. He says the larvae are likely somewhere in the soil, eating the roots of (other) plants.

Update: Ted kindly pulled some strings among his beetle expert friends. Here’s his report:

According to my friend, Arthur V. Evans, an expert in the family Scarabaeidae, the beetle in your photos is Magnus bolax of the subfamily Rutelinae (closely related to the Melolonthinae). I could not find any particular information about this species other than collection listings and various checklists; thus, its occurrence as a defoliating pest of your Calathea lutea seems to be a one-off thing. A nice picture of a mating pair can be seen on page 6 in the September 2007 issue of SCARABS, a newsletter devoted to the study of scarab beetles.

Magnus bolax is one of 541 species of scarab beetles that have been recorded from Panamá (Ratcliffe 2002) it is a hugely diverse family.

P.S. Another interesting factoid I forgot to mention  – the Latin word from which the genus name is derived means “large”, while the meaning of the specific epithet is “lump” – this beetle’s name means, literally, “large lump”.  I find that immensely amusing!

Ted’s note that this beetle is not known as a defoliating pest is supported by Carla Black, who has lived and observed in Panama for some years. Here’s what she had to say about la plaga:

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