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| The strikingly patterned eyed click beetle (Alaus oculatus) (Cary, NC). |
It would be nice if all arthropods were as distinct as eyed click beetles (Alaus oculatus; above), harlequin bugs (Murgantia histrionica) or black and yellow orb weavers (Argiope aurantia). Although it would put me out of a job, it would also allow the public to better understand what insect, spider or millipede they are looking at in their garden or on their kitchen counter.
Alas, many arthropods are difficult to identify or even impossible, especially just looking at them briefly. For example, in some species the male genitalia is the deciding characteristic - this makes female specimens unidentifiable to species or even genus. Others have many look-alikes or have not been well studied enough to find diagnostic traits to separate species. While these organisms may be very easily identified by experts, the public has very little chance of coming up with a name for the creature in question.
Some groups, however, are like black holes even to experts. I am sure every diagnostician can think of the group or groups in their field that have this characteristic. Among arthropods, I can think of a few:
- small to medium brown moths (Lepidoptera)
- acalyptrate flies (most Cyclorrhapha)
- many small, parasitic wasps (Chalcidoidea & Platygastroidea)
- ground "sac" spiders (Clubionidae, Corrinidae, Gnaphosidae, Miturgidae...)
These groups share one thing in common: they all have many members which cannot easily be told from one another superficially, or at the very least from just looking at a photo online.
The idea of blogging about this came to me last week when I got two samples into the clinic with superficially similar little brown beetles (another of these tough groups, and probably one of the most difficult).
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| Can you tell them apart? LBBs (Little Brown Beetles) representing 3 families and 2 superfamilies. Left - Mycetophagidae: Typhaea stercorea (Tenebrionoidea); Middle - Silvanidae: Ahasverus sp. (Cucujoidea); Right - Erotylidae: Cryptophilus sp. (Cucujoidea). All from North Carolina, USA [Photo by Matt Bertone] |
One species (above left) was from garlic that had been left in a barn to cure after harvest. The other two (above middle & right) were found as adults and larvae in alfalfa hay. All three beetles were likely attracted to the fungus that was growing on these drying products which probably grew mold due to the humid and rainy weather we have been getting. All three are functionally similar, but taxonomically very different. There are over a dozen such families of small, brownish beetles that act very similar, infesting stored products, dried wood, and moldy areas (just look at some Cucujoidea to see how similar some are). Many are thus associated with human homes and product facilities where they feed either directly on the grains or on the microscopic molds that coat these products. Not only are they difficult for the layperson to identify, but most are also small to extremely small, making ID even more difficult:
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| Actual size of the beetles shown above. The largest (Left) tops out at just under 3 mm long! [Photo by Matt Bertone] |
In the end, these arthropods are what keep people like me busy looking at them under a microscope at 70X magnification, counting the number of segments in their feet...