Holometabolous When?

A few days ago, I asked you to guess the problem with this T-shirt (from here):

'Holometaboly' refers to the life-cycle found in insects belonging to the clade Holometabola (i.e. flies, moths, wasps, beetles, etc.), where the larval stage is significantly different in appearance to the adult stage, and the body undergoes significant reconstruction during an intervening, quiescent pupal stage. Some of you may be aware that thrips are not members of the clade Holometabola, being instead more closely related to the Hemiptera, the sucking bugs. Nevertheless, thrips can indeed be described as holometabolous, as they have evolved a pupal stage in their life cycle independently of the holometabolans. So my problem with the slogan 'Holometabolous before it was cool' is not with the use of the word 'holometabolous'.

It's with the word 'before'. The earliest known crown-group thrips, and thus the earliest known thrips that we can be reasonably certain was holometabolous (absent actual fossilised thrips pupae) is Liassothrips crassipes from the Late Jurassic (Shmakov 2008). In contrast, the earliest known crown-group holometabolans are stem-beetles and stem-neuropterans from the Early Permian, a good hundred million years or so before (Grimaldi & Engel 2005). Even if we open the gates to potential stem-group thrips (which may or may not have been holometabolous), that doesn't take us back any further than a potential tie with the Holometabola.

Liassothrips crassipes, from Schmakov (2008). Scale bar equals 1 mm.

So while thrips may be holometabolous, the possibility that they were so 'before it was cool' is fairly remote. Thrips are much more likely to have been late-comers to the holometaboly game.

REFERENCES

Grimaldi, D., & M. S. Engel. 2005. Evolution of the Insects. Cambridge University Press.

Shmakov, A. S. 2008. The Jurassic thrips Liassothrips crassipes (Martynov, 1927) and its taxonomic position in the order Thysanoptera (Insecta). Paleontological Journal 42 (1): 47-52.