Roles of insects in the mesozoic ecosystems of Northeastern China

Insects have been in existence for at least 400 million years. These relatively small-sized terrestrial arthropods, along with their durable cuticle, have allowed them to be preserved in compression fossils and ambers. Based on insect fossils collected in northeastern China (i.e. Liaoning, Inner Mongolia and Hebei), at least 19 orders and nearly 300 species have been reported (Ren et al. 2010). Paleoentomology in China have made significant progress in recent years.

Many insects have close interactions with plants, which are recorded on fossils. For example, Protonemestrius jurassicus had long siphonate mouthpart, suggesting its “flower” visiting habits, which is important for the study of the origin of angiosperms (Ren, 1998). A probable pollination mode before angiosperms was proposed based on the Eurasian, long-proboscid fossil scorpionflies from the Middle Jurassic to the Early Cretaceous, which fed on ovular secretions of extinct gymnosperms and engaged in pollination mutualisms with gymnosperms (Ren et al. 2009). Two extraordinary fossil lacewings demonstrated a preangiosperm origin for leaf mimesis, revealing a lost evolutionary scenario of interactions between insects and gymnosperms (Wang et al., 2010). Lately, a near-perfect mimetic association and potential mutualism between a mecopteran species and a ginkgoalean plant species from the late Middle Jurassic of northeastern China has been discovered, suggesting that hangingflies developed leaf mimesis either as an antipredator avoidance device or possibly as a predatory strategy to provide an antiherbivore function for its plant hosts (Wang et al., 2012). Besides feeding on leaves and plant matters, a katydid, Archaboilus musicus was reported to produce low-pitched musical songs, which are well-adapted to communication in the mid-Jurassic forest with coniferous trees and giant ferns (Gu et al. 2012).

On insect association with vertebrates, two well-preserved fossil ectoparasitic insects have been found in the mid-Mesozoic of China, exhibiting many features of ectoparasites. Large body size and long serrated stylets for piercing tough and thick skin or hides of hosts suggest that these primitive ectoparasites might have lived on and sucked the blood of relatively large hosts, such as contemporaneous feathered dinosaurs and/or pterosaurs or medium-sized mammals (Gao et al., 2012). A new transitional flea, Saurophthyrus exquisitus, has a series of translational characters in between those of Pseudopulicidae and living fleas suggesting it might have lived and fed on blood of the pterosaurs or other host vertebrates (Gao et al., 2013).

Based on the coexisting plants and other animals, we established a structure of the ecosystems of the Yanliao Biota and Jehol Biota respectively. Insects played important roles in maintaining food chains and ecological successions, in circulation of substances and global flow of energy.