Earliest Known Stick Insect Fossils Discovered in China
Paleontologists led by Dr Maomin Wang from Capital Normal University in China say the newly discovered stick insect Cretophasmomima melanogramma may have mimicked plant leaves for defense at least 126 million years ago.
This is a reconstruction of stick insects Cretophasmomima melanogramma and a prehistoric rodent among gymnosperm plant Membranifolia admirabilis. Image credit: Wang M et al.
Many insects have developed defense mechanisms, including the ability to mimic the surrounding environment.
Stick and leaf insects (Phasmatodea) mimic plants from their environment. Fossil species that can be conclusively identified as stem-relatives of stick- and leaf-insects are extremely rare.
The fossil stick insect Cretophasmomima melanogramma has been described on the basis of one female and two male specimens collected from the early Cretaceous of the Jehol locality in Inner Mongolia, China.
Three specimens of Cretophasmomima melanogramma. Image credit: Wang M et al.
Cretophasmomima melanogramma possessed adaptive features that make it resembling a plant recovered from the same locality. Its wings have parallel dark lines and when in the resting position, likely produced a tongue-like shape concealing the abdomen.
Fossils from the gymnosperm plant Membranifolia admirabilis have been documented in the area with similar tongue-shaped leaves along with multiple longitudinal lines.
Dr Wang and colleagues said the insect used this plant as a model for concealment.
Specimens of the gymnosperm Membranifolia admirabilis. Image credit: Wang M et al.
“The new fossils indicate that leaf mimicry was a defensive strategy performed by some insects as early as in the early Cretaceous, but that additional refinements characteristic of recent forms, such as a curved part of the fore legs for hiding the head, were still lacking,” said the authors, who reported their findings in the journal PLoS ONE.
“They suggest that leaf mimicry predated the appearance of twig and bark mimicry in these types of insects. The diversification of small-sized, insect-eating birds and mammals may have triggered the acquisition of such primary defenses.”