BIOTIC INTERACTIONS OF INSECTS WITH PLANTS AND OTHER ASSOCIATES IN TWO MID MESOZOIC ECOSYSTEMS OF NORTHEASTERN CHINA

Although the Early Cretaceous Yixian and Middle Jurassic Jiulongshan Formations of Northeastern China have yielded well-preserved vertebrates, it is insects that have provided the greatest amount of autecologic data. We present eight categories of biotic interactions involving seven insect orders interacting with coexisting plants, other insects and vertebrates. First, the long-proboscid pollination mode is a pollinator mutualism by three families of Mecoptera that evolved convergent siphonate mouthparts for imbibition of pollination drops from tubules or channels in gymnosperm ovulate organs. Second, mimesis, or camouflage, was present in two lacewing taxa that imitated co-occurring pinnate gymnosperm pinnules. Similarly, a scorpionfly mimicked an entire co-occurring ginkgo leaf, presumably providing protection to plant model and insect mimic. Third, considerable insect damage is recorded on a variety of plants involving galls by Coleoptera and stylate punctures and margin feeding, probably by Hemiptera and Orthoptera, respectively, among others, on vascular-plant tissues. Fourth, integumental blood feeding was established by ectoparasites such as a basal lineage of fleas (Siphonaptera) that possessed long stylets consisting of robust, outwardly directed, serrated stylets, and bugs (Hemiptera) involved in piercing thick vertebrate integument and imbibing host blood and possibly lymph. Fifth, parasitoid larvae, especially highly diverse apocritan wasps such as Ephialtitidae and Pelecinidae (Hymenoptera) consumed the integument and body cavities of other host arthropods. Sixth, predatory feeding by diverse insects, such as hangingflies (Mecoptera) and mantispids (Neuroptera) were equipped with prey-neutralizing devices. Seventh, two genera of Mecoptera with exaggerated male organs, likely representing the earliest example of long-term male‒male competition in insects. Eighth, reproduction was highlighted by a pair of copulating froghoppers (Hemiptera), hitherto the earliest record of copulating insects in flagrante delicto. These eight, intricate, mid-Mesozoic associations provide an expanded understanding of the ecologic role and necessary evolutionary developments that insects had in mid-Mesozoic ecosystems.