I was all set to make a “One-Shot Wednesday” post today, but sometimes big news strikes and plans must change. The news today was in the form of a random tweet by Alex Wild:
The link in the tweet led me to the following photo on iStock by Getty:
bedbug has captured worm
I was stunned—the photo depicted a scene almost identical to one that I had photographed back in September while visiting soybean fields in Louisiana. For two months I sat on the photo with no idea what I was looking at, but now thanks to Alex I have my answer! Compare the above photo with mine below, and you’ll see that everything matches perfectly—I had photographed a “bedbug” that had captured a “worm”!
bedbug captures a worm
I considered myself to be fortunate, because there was not just one but two different subjects in the photo, and both of them matched perfectly with the subjects shown in the iStock photo. Gotta love the internet—nowadays names for even the most hard-to-identify bugs are just a click away if you know where to look!
</snark>
Of course, the aggressor in both photos is not a “bedbug” [sic for “bed bug”] (order Hemiptera, family Cimicidae) but a stink bug (family Pentatomidae), specifically Podisus maculiventris, or “spined soldier bug”—perhaps the most common predatory stink bug in North Amerca and ranging from Mexico and parts of the West Indies north through the U.S. into Canada. It is a well-known predator of crop pests and, as such, has been imported to several other countries as part of classical biological control efforts. As for the “worm,” in my photo it is a late-instar larva of Chrysodeixis includens, or “soybean looper, and while I haven’t been able to identify the exact species in the iStock photo it is definitely a lepidopteran caterpillar that appears to related to if not in the same family as the soybean looper (Noctuidae). Now, I concede that “worm” is sometimes used for lepidopteran larvae, but one must also concede that in it’s broadest sense “worm” can refer to members of several disparate phyla such as Nematoda (roundworms), Platyhelminthes (flatworms), or Annelida (segmented worms).
This case, of course, just screams for application of the Taxonomy Fail Index (TFI), which scales the amount of error in a taxonomic identification in absolute time against the error of misidentifying a human with a chimpanzee—our closest taxonomic relative. For example, when TFI = 1 the error is of the same magnitude as mistaking a human for a chimp, while TFI > 1 is a more egregious error and TFI < 1 a more forgivable one. In the case shown here, one must go back to the common ancestor that eventually gave rise to all of the worm phyla and noctuid moths (~937.5 mya). In addition, since there are two subjects in the photo, one must also go back to the divergence of the main hemipteran groups that contain bed bugs and stink bugs (mid-Triassic, ~227.5 mya). This results a whopping 1.165 billion total years of divergence between the identifications assigned to the subjects in the iStock photo and their actual identity. Assuming that chimps and humans diverged approximately 7.5 mya, this gives a TFI for the iStock photo of 155! I haven’t searched thoroughly to determine whether this is a record for the highest TFI in a single photo, but surely it is a strong contender!
Copyright © Ted C. MacRae 2013
Beetles In The Bush 
Taxonomy Fail Index — I so have to start using that metric in my QC work!
I’ll bet you’ve got some whoppers.
A few, yes. Several of which I shouldn’t share in public!
So I was thinking that maybe the TFI should be weighted somehow when taxonomic experts are involved in the fail. Consider the case of the caddisfly Helicopsyche borealis whose larvae were first described as snails (Lea, 1834). By my calculations, that should yield a TFI = 78.1. Or what about water penny larvae (Psephenidae) originally being described as Isopoda? TFI = 59.1.
Greater level of error in “bed bug” than in “worm” because of the noted imprecision in that word. Noctuid caterpillars themselves are referred to as “cutworms”
Well, some noctuids are called cutworms; there are also armyworms, earworms, bollworms, podworms, fruitworms, budworms, leafworms, webworms, grassworms (takes big breath)… 🙂
And also, and this is in no way meant as a criticism, but simply sharing a life experience and point of view. As I have gotten older (I’m 60) I have tried to be patient with anyone who shows any interest in the natural world, and attempt to encourage their interest by helping them identify species to whatever level I can. I know from personal experience that Ted is this way, too. No matter how much more about insects than the average person any of us knows, our knowledge is dwarfed by our ignorance, whether compared to the overall knowledge science as a whole has gained, or the even greater knowlege that is yet to be achieved.
Of course, but in this case what Alex said.
Wow! What an interesting post. Although my brain cannot quite wrap itself around how TFI works completely. Its a little early… 🙂
Last common ancestor of chimps and humans lived about 7.5 million years ago, but last common ancestor of bed bugs and stink bugs lived about 227.5 million years ago. 227.5 divided by 7.5 = 30.3 – in other words mistaking a stink bug for a bed bug is 30.3 times worse than mistaking a human for a chimp. Really, it’s just a fun way for biologists to feel superior 🙂
That makes sense now and is CRAZY! Interesting. Thanks for explaining it 🙂
Cool – good to know I can actually explain it clearly 🙂
While I can see Harry’s point, this is a case where I suspend niceness.
iStockphoto is a professional stock image site. The photographer is not a hobbyist, but a person who uploaded the photograph with the intent of being paid for it. The photographer has a position of responsibility here, and has abrogated it by not correctly identifying the subject matter.
Totally.
I wasn’t paying attention at first, so I spent half the post thinking: ‘that is some strange bed bug and worm you got there… Now I get it. Taxonomic Fail Index, I love it!
I love it when people fall for my snark – however briefly.
Haha!