Party on a pin oak

In September 2012 while collecting in western Oklahoma (Weatherford) I came across this interesting scene. It had been exceedingly dry in the area, and because of this few insects were out and about in the small city park that I stopped by to check for the presence of tiger beetles. I had nearly completed my circuit of the park when I came upon a moderate-sized pin oak (Quercus palustris) tree and noticed something on the lower trunk:

Six insect species representing five families in four orders share a sap flow.

Six insect species representing five families in four orders share a sap flow on the trunk of a pin oak.

No less than six insect species representing four orders were seen all huddled together at a darkly stained sap flow. This could be the result of slime flux, a bacterial disease that usually affects deciduous hardwoods that are under stress and results in darkly stained weeps on the trunk that are known to be attractive to a variety of insects. At the center sat a green June beetle (Cotinis nitida) and three bumble flower beetles (Euphoria inda)—all in the family Scarabaeidae (subfamily Cetoniinae). Covering the scarab beetles were half a dozen Texas Tawny Emperor (Asterocampa clyton texana) butterflies (family Nymphalidae, or Brushfooted Butterflies), and milling around the perimeter was a velvet ant (Dasymutilla creusa, I believe) in the family Mutillidae, an apparent flesh fly (family Sarcophagidae), and a true ant (family Formicidae). I guess this would be the equivalent to a watering hole in Africa with a lion, a hyena, a baboon, three vervet monkeys and six zebras all crouched shoulder-to-shoulder at its edge.

Euphoria sepulchralis feeds on a sap flow higher up on the trunk.

Euphoria sepulchralis feeds on a sap flow higher up on the trunk.

Further up on the trunk, yet another species of scarab beetle, a dark flower scarab (Euphoria sepulchralis) was found feeding on a smaller sap ooze. Unlike the diverse aggregation of insects on the lower ooze, this guy had managed to keep the ooze all to himself.

Cotinus nitidus | Weatherford, Oklahoma

Cotinis nitida | Weatherford, Oklahoma

Green June beetles, especially, are known for their feeding on sap oozes. The beetles are actually attracted to the odors caused by fermentation of the sap rather than the sap itself. It has been reported that the presence of alcohol in fermenting sap can affect the behaviour of insects that feed upon it, causing them to act “stupid and lethargic.” I did not see any such behavior, but I did notice that the insects were not at all skittish and loath to leave the sap.

Copyright © Ted C. MacRae 2013

9 thoughts on “Party on a pin oak

  1. Seeing the Euphoria sepulcralis in your post reminds me that I used to sell these to a biological supply company (forget which one) that charged $4 apiece for carded specimens. I could find drowned Euphoria by the hundreds in our swimming pool in Miami, so I was pretty surprised that they could get that much for them. They offered me only $1 each for them wrapped and labeled, but it was still worthwhile because they offered to pay me in trade for other beetles I couldn’t find in Florida. It took some work, but that’s how I got a pair of Dynastes granti plus Chrysina gloriosa for my collection. Ha! My motto is, “Will work for beetles.”

    • Geez, $4 a piece? I run into that species quite often, especially in the fall on goldenrod flowers. I wonder who’s buying them? I don’t know, I just don’t get much enjoyment out of buying/selling bugs – seeing them in the field is so much more enjoyable. That said, I’ll gladly buy or trade for Buprestidae, where I’m trying to maximize the taxonomic representation as much as possible.

      • These are the only beetles I ever sold, and I only did that because they were already dead. In fact, I quit actively collecting because I felt bad about killing insects for that purpose alone. The last beetle I almost collected was an Eyed Elater, the first I had seen in Florida, but I worried about reducing an already thin population; I released it. I started feeling that way about 35 years ago when I collected a Deltochilum gibbosum from a pile of wild hog dung. I haven’t found another one of those since. Like you, I much prefer to photograph live beetles.

        • Just to be clear, I meant that I prefer acquiring insects by collecting them in the field myself over purchasing/exchanging for them, not that I prefer not to collect them. There are many reasons to collect or not collect, but the last reason for not collecting is because of concern over impacting populations. While it is true that this is possible in very special cases (extreme specialists of relictual, upland habitats with very low vagility), it is mathematically impossible to overcollect the vast majority of insect species—even “rare” species (which is usually an artifact of incomplete knowledge rather than actual rarity—population genetics requires a minimum population size of at least several hundred individuals to even remain viable, and almost never is more than a tiny fraction of an insect species’ total population even accessible for collectors to begin with). I don’t say this to argue that everybody should be collecting, only that this should not be a reason for not doing so. Truth is, amateur collectors have made a significant contribution to knowledge of the world’s insect fauna. Even if they themselves did nothing more than assemble the collection, the material still usually ends up in a public museum and available to researchers who utilize it for their studies.


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