Spam (madbodger) wrote,
Spam
madbodger

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Beetles

I noticed that something was eating our Solanum pyracantha the other day, which was both annoying and surprising. Surprising because these plants are amazingly unfriendly plants, with hairs, thorns, and every single part of the plant is poisonous. It’s a member of the large deadly nightshade family, and contains solanine, a poisonous glycoalkaloid especial to these plants, as well as atropine-like alkaloids and saponins.

So I wondered what bugs these were that were eating this deadly conconction with impunity. Looking at them revealed that they were tiny beetles, which narrowed it down somewhat (Kingdom Animalia [animals], Phylum Arthropoda [arthropods], Class Hexapoda [insects], Order Coleoptera [beetles]) fairly quickly1. But beetles are a huge group, and I had exhausted the taxonomic data I carry around in my head.

A little research revealed that they were probably flea beetles (Superfamily Chrysomeloidea [long-horned and leaf beetles], Family Chrysomelidae [leaf beetles], Subfamily Alticinae [flea beetles]2. But here I was rather stuck. Flea beetles are tiny and the Subfamily contains many genera. There is a handy identifying key on the web that allows you to make binary choices in order to arrive at a genus.

But even armed with this photomicrograph I made (the lines at the bottom are millimetre marks on a ruler, to give scale), I wasn’t up to deciding whether or not this beastie had the posterior part of its prosternum triangularly excavated, so I had to resort to another tactic. Happily, the web came to my rescue again, with a list of flea beetles, along with the plants they inhabit. It seems our little poison eater should be in either Genus Ochrosis or Epitrix. As Ochrosis contains a single species (ventralis) which is orange, and does not occur in North America, it would seem that Epitrix is our perpetrator. I’m stymied as to the species, but it doesn’t matter.

A few days later, I was gardening with red_lynx and keith_m043 and removing some vines that were all over some Russian sage. On the underside of one of the leaves, I found a pair of mating beetles, with a gorgeous metallic gold color. Not just a shiny yellow, they actually looked like drops of molten gold. The theory was advanced that they were juvenile June bugs, but I doubted it, as juves don’t mate. Also, keith_m043 suggested that the colour wasn’t pigment based, but a structural interference pattern, like the colour of Morpho butterflies. It turns out that these are Aspidomorpha tecta, more leaf beetles. They live on morning glory vines, which red_lynx confirms is what the vines were. And keith_m043 is right, the colouration is due to broadband interference from a structure known as a "chirped stack".

1 It seems I had misremembered even that bit, as Hexapoda is a Superclass, containing class Insecta, which in turn contains Subclass Pterygota (winged insects).
2 I also missed Suborder Polyphaga (water, rove, scarab, longhorn, leaf, and snout beetles), and apparently Alticinae are now considered a tribe (Alticini) of Galerucinae, but this is contentious. *shrug*

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