Cretaceous beetle attack

Following last month’s item on vast moth beds in Denmark, yet another bizarre result of painstaking palaeontological research has surfaced in the July 14 issue of Science.

Palaeobotanist Peter Wilf of the University of Michigan, and colleagues, have collected extensively from the late-Cretaceous and early Tertiary terrestrial sediments in Wyoming and North Dakota.  Among their specimens of early angiosperm (flowering plants) leaves are a number showing evidence of insect damage.  The authors matched chew marks on what are probably ancestral leaves of the ginger plant with those of living beetles.  Amazingly, Wilf and co. showed that the damage is near-identical to that created by larvae of rolled-leaf beetles that still prey on the ginger plant (Wilf, P. et al., 2000.  Timing the radiations of leaf beetles: hispines on gingers from latest Cretaceous to Recent.  Science, v. 289, p 291-294).  Larvae take up residence in the curled, young leaves of gingers.  The young beetles then chew leaf tissue in highly distinctive patterns.  Only when the leaves unfurl do the bite marks reveal themselves, the beetles being long gone.

Curled-leaf beetles are extraordinarily loyal to their favourite plants among the gingers and heliconias, so that beetle-plant pairings generally involve only one beetle- and one plant species   Quite probably beetles and other insects underwent an evolutionary explosion at the time of the radiation of the angiosperms, because of the diversity of forms and metabolic pathways followed by flowering plants compared with other members of the Plant Kingdom.  The find helps confirm the hypothesis proposed by insect evolutionist Brian Farrell of Harvard University, that most plant-eating beetles evolved in parallel with flowering plants.


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