Insects of a Lost World

The Jurassic period is often associated with dinosaurs, but it was equally significant for insects. During this time, insect diversity reached new heights, beetles became the most species-rich order, and remarkable examples of convergent evolution appeared — most notably the Kalligrammatidae, lacewings that evolved to look and function almost exactly like butterflies, over 50 million years before true butterflies existed.

The Jurassic World

Pangaea began to break apart during the Jurassic, with the Atlantic Ocean starting to open. The climate was warm and humid, with no significant polar ice caps. Vegetation was lush, dominated by conifers, ferns, cycads, ginkgoes, and bennettitales. Flowering plants had not yet appeared (or were present only in very early, inconspicuous forms).

Oxygen levels were higher than in the Triassic, estimated between 20-26%, creating favorable conditions for insect diversification, though not at the extreme levels of the Carboniferous.

Fossil sites like Solnhofen in Germany and Karatau in Kazakhstan preserve rich Jurassic insect faunas in fine-grained limestone, giving us detailed windows into these ancient ecosystems.

The Beetle Explosion

Coleoptera (beetles) diversified enormously during the Jurassic. Several modern beetle families first appear in the Jurassic fossil record, including early weevils, jewel beetles, and click beetles. The success of beetles is often attributed to their adaptable body plan, the protective elytra (hardened forewings), and their ability to exploit wood, fungi, and plant tissues as food sources. By the end of the Jurassic, beetles were already the most species-rich insect order — a distinction they hold to this day. See Insect-Plant Co-Evolution for context on how plant relationships drove beetle diversity.

Convergent Butterflies: Kalligrammatidae

One of the most remarkable stories in insect evolution is the Kalligrammatidae, a family of lacewings (Neuroptera) that evolved large, broad wings with eyespots, a coiled proboscis for feeding on plant fluids, and likely engaged in flower visitation — all characteristics that we associate with butterflies. Yet true butterflies (Lepidoptera) would not evolve these traits for another 50+ million years. This is a textbook example of convergent evolution: two unrelated groups independently evolving very similar forms and behaviors in response to similar ecological pressures.

Giant Cicadas and Other Notable Groups

The Palaeontinidae were large hemipterans resembling enormous cicadas, with wingspans up to 15 cm. They had piercing mouthparts and likely fed on the sap of Jurassic conifers and other gymnosperms.

Strashila is one of the strangest Jurassic insects — a bizarre, possibly parasitic creature known from the Karatau deposits. Its exact affinities and lifestyle remain debated, illustrating how alien some prehistoric insects were compared to living forms.

The Hymenoptera (the order that includes modern wasps, bees, and ants) also diversified during the Jurassic. Parasitoid wasps, which lay their eggs in or on other insects, became increasingly common. This represented a new and highly effective ecological strategy that would drive arms races between parasitoids and their hosts for the rest of insect evolutionary history.

Insects and Dinosaurs

Jurassic insects and dinosaurs shared ecosystems, but direct interactions are rarely preserved in the fossil record. However, the presence of blood-feeding insects (early parasitic flies, for example) and copious insect herbivory on Jurassic plants suggests that insects were interacting with dinosaurs in many of the same ways that modern insects interact with large vertebrates — as parasites, pollinators of their food plants, and decomposers.