The puzzling case of the twisted sisters

In the business of making evolutionary trees you’re always on the lookout for a conundrum. After-all, what’s fun about solving a puzzle with only 10 pieces? Sure it’s easy. It’s got that going for it. But we enjoy puzzles precisely because they are hard.

That’s what the tree making business is about: solving the hardest puzzles of life. Literally, puzzles of life. Not puzzling issues about your life but putting together the pieces that tell the story of how life evolved.

There’s a few ways that a good phylogenetic (fancy word for evolutionary) tree puzzle can be found. Some of those ways have to do with the troubles of very close relatives (like my last blog), and some of those have to do with the troubles of very distant relatives. This story is a puzzle about the latter.

There are these odd little insects.

A twisted wing parasite a.k.a Strepsiptera

They live most of their lives as babies inside of other insects. They are parasites that feed on their host. As adults they cannot feed, and use their mouths for sensation only. They have sex through hypodermic insemination (which is as vile as it sounds) and the offspring are born when they consume their mother from the inside out. They are called twisted wing parasites, which is purportedly a reference to how they hold their wings, but I cannot help but believe “twisted” refers to their moral character.

Confusing right from the start

When the first species was discovered in 1793 no one knew what they were. First they thought they were maybe a type of parasitic wasp. After all they are parasites, and who’s to say they don’t look terribly wasp-like? A fella’ named Kirby named another species in 1802 but didn’t even realize it was related to the first one they discovered. Good job by Kirby. Another dude, Latreille, then decided that they should probably be flies since, like flies, they have only 2 wings. Kirby, in an attempt to redeem himself, did a more thorough analysis and said that they weren’t flies, nor were they wasps. They were their own thing that he dubbed “Strepsiptera” (which means “twisted wing”). But Kirby failed to tell us Strepsiptera’s closest relative. So again, epic fail (to be fair, Darwin hadn’t even published his great work yet so it’s unclear that these guys even believed that these animals derived by common descent, in fact they probably didn’t). Lamarck, who believed that orangutans evolved long arms by swinging them around all day, took a stab at it and agreed with Latrielle-they were flies. Latrielle, not to be outdone by Lamarck or Kirby, also decided these little bugs were their own thing but called them by a different name, just to be a dick. (This history is taken from Whiting et al 1997 with my own added flair).

This non-sense continued for the rest of the century. The twisted little fellas went back and forth between being wasps, true flies, dragonflies, butterflies, mayflies, and back to true flies again. Then the century turned. World War 1 was right around the corner. The humble beginnings of the roaring 20’s were happening across America. The number 9 was about to be a new favorite on the printing press. Times were changing! And it was time for twisted wing insects to be put into a new group altogether: beetles!

These are adult Strepsiptera and their bee hosts. Must not feel too good to have that thing inside of you.

Although to be honest, the story of the 1900s wasn’t much different than the story of the 1800’s. Twisted wing insects bounced in and around the beetles, back to flies and for a brief moment outside the true metamorphic insects all together (Kristensen 1991) and then back to flies (Whiting & Wheeler 1994).

In comes Mr. Professional Phylogeny Maker Man. His idea was to solve this problem by looking at their DNA. If their physical form was confusing people he thought to look at genes that have nothing to do with physical form. In fact he looked at genes make things that work inside the cells. That should solve the problem!

Turns out this wouldn’t solve the problem. In fact this was an issue until this very decade (Trautwein et al 2012; Ishiwata et al 2011). Well, actually this is still going on because I’m sure there are people who won’t accept the most recent studies (Ishiwata et al 2011; Misof et al. 2014).

And to be honest they shouldn’t accept it. Not because it’s wrong but because we aren’t sure that it’s right. We won’t be until study after study shows the same thing. We’re on that path (or close to this) but we’re not there yet.

So, what are twisted wing insects? Who are their twisted relatives? Do you really want to know?

The answer to the puzzle and surrealism in film

One of the major things that made the puzzle so hard was that the DNA (Gillespieet al. 2005; Ishiwata et al. 2011) and the morphology (Kristensen 1991) were both so different from anything else that it was really difficult to figure them out. In technical terms we call this “long branch attraction”. It sounds lovely but it’s the bane of systematists everywhere.

Allow me to make a bit of a crazy analogy to explain what long branch attraction is.

Have you seen the movie Lost Highway? If you haven’t, it’s different from almost any other movie you have ever seen. So different, in fact, that it makes almost no sense what so ever. One of my favorite films is a Japanese movie called Gozu. Although, these two movies are culturally, thematically and produmoviesctionally unrelated I cannot help but lump these two movies together. I would say, “If you like Lost Highway, then you will LOVE Gozu”.


Lost Highway is a story about infidelity. It involves some kind of demonic figure, time travel and possibly multiple dimensions; although to be honest I’m not really sure (the movie is pretty confusing). Gozu is about a gangster who loses his brother, only to find that he is reincarnated as an attractive woman whom he falls in love with. Ok, there’s a lot of driving around in both but believe me, these two movies are extremely different. Then why do I insist they are related? Precisely because they are so different!

This is more or less the same thing as long-branch attraction. When two living things (or movies) are so distantly related from any other living thing (or movie), they appear to be closely related to each other. However, the similarities they share are just a result of them having lots of random differences that end up matching by chance, just like Lost Highway and Gozu.

NOTE: I insist this analogy makes sense, although I did not do a thorough, in-depth researching of the movies in question. So lend me a little slack if your film critiquing skills exceed mine. And YES, I’m sure you could argue that Takeshi Miike was influenced by David Lynch, but I argue that this is horizontal transfer rather than vertical relatedness…….just let me make my point ok?

Lost Highway is like Strepsiptera and true flies are like Gozu.

So who the hell are the twisted sisters-the most closely related insects to Strepsiptera?! They are now thought to be their own thing closely related to beetles, but not beetles themselves. I guess that would make beetles the movie Blue Velvet.

Twisted wing parasites…more twisted than we thought.



Dominic Evangelista is a PhD candidate studying the biodiversity and systematics of the cockroaches of the Guiana Shield. Follow him on twitter @Roach_Brain or ask him a question about cockroaches!

Works cited:

Whiting MF, Carpenter JM, Wheeler QD,WheelerWC.1997. The Strepsiptera problem: phylogeny ofthe holometabolous insect orders inferred from 18S and 28S ribosomal DNA sequences and morphology. Syst. Biol. 46:1–68

Whiting MF, Wheeler WC. 1994. Insect homeotic transformation. Nature 368:696

Trautwein MD, Wiegmann BM, Beutel R, Kjer KM, Yeates DK. 2012. Advances in insect phylogeny at the dawn of the postgenomic era. Annu Rev Entomol 57:449-468.

Ishiwata K, Sasaki G, Ogawa J, Miyata T, Su ZH. 2011. Phylogenetic relationships among insect orders based on three nuclear protein-coding gene sequences. Mol Phylogenet Evol 58:169-180.

Misof B, Liu S, Meusemann K, Peters RS, Donath A, Mayer C, et al. 2014. Phylogenomics resolves the timing and pattern of insect evolution. Science 346:763-767.

Gillespie JJ, McKenna CH, Yoder MJ, Gutell RR, Johnston JS, Kathirithamby J, et al. 2005. Assessing the odd secondary structural properties of nuclear small subunit ribosomal rna sequences (18s) of the twisted-wing parasites (insecta: Strepsiptera). Insect Mol Biol 14:625-643.