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Oldest stick insect ever known found in Mongolia

Maomin Wang from Capital Normal University in Beijing, China and colleagues from China, France, and Germany reported the discovery of the oldest known fossil stick insects ever found in the March 19, 2014, edition of the journal Public Library of Science.

Renphasma sinica Nel and Delfosse, 2011.
Renphasma sinica Nel and Delfosse, 2011.
Wang et al. doi:10.1371/journal.pone.0091290.g001
At left: Cretophasmomima melanogramma at right: Membranifolia admirabilis.
Credit: left: O. Béthoux, right: F. Jacques Usage Restrictions: left: O. Béthoux, right: F. Jacques

One female and two male specimens were recovered from the 126 million-year-old Yixian Formation in Inner Mongolia. The new stick insect species was named Cretophasmomima melanogramma.

Cretophasmomima melanogramma females were 56 millimeters in length and males were 50 millimeters in length. A characteristic ‘shoulder pad’ on the fore wing defined the insects as a true ancestor of present stick insects.

A series of parallel dark lines on the insect’s wings was found to be extremely similar in shape and size to the markings on the leaves of a relative of the ginkgo plant that was found in the same area and dates from the same time period.

The markings indicate that adaptations for defense by imitation of leaves predated any adaptation that involved imitation of stems or branches in insects as a defense mechanism.

The conclusion is consistent with the plant fossil record at the time Cretophasmomima melanogramma lived in the part of Mongolia where the fossils were found.

These fossils are the oldest known insect that imitated plant parts as a means of defense from predators.