An entomological guide of the trample steppe

Thanks to its increased plant and animal biodiversity, the trample steppe is a paradise for many types of invertebrates, especially insects. In this biome, the number of species of pollinators is significantly higher compared to the coldvanna, encompassing hundreds of species of flies, butterflies, moths, wasps, and bees that collect nectar from various types of flowers. Beetles also play a crucial role as pollinators in Antarctica, particularly a specialized species known as the weeeevil (Floricurculio longicephalus). As the name suggests, the weeeevil is a type of coleopteran belonging to the Curculionidae group, the most diverse family of animals. It retains many basal features typical of these insects but presents several anatomical autapomorphies. One of the distinctive features of the weeevil is its head, markedly different from its ancestors: instead of developing a long proboscis for nectar consumption, the weeeevil possesses a long snout and a relatively short proboscis. This characteristic aligns with their pollination strategy, wherein their antennae serve as the primary organ to transport pollen. These feather-like antennae, situated in the upper part of the head, effectively trap pollen when the animal inserts its head into a flower. The proboscis is reserved solely for extracting nectar from the base of the flower.

The weeevil is not the sole fascinating pollinator in the trample steppe. The diverse group of pollinators also includes a species of ants called waxant (Mellithorax antemnimanus), known for its highly specialized nectar-based diet, although they still integrate their diet with animal carrion. They live in relatively small social groups, that rarely exceed 1500 individuals and they are known to collect and produce wax, similar to bees. However, this wax is not only intended for honey collection but also for thermally isolating the ground cavities where they reside. Unlike bees, which store honey inside cells, waxants stored it instead inside large cupped "granaries", which are well isolated from the soil with wax in order to reduce cleptoparasitism from other ant colonies and fossorial insects. They are known to use their robust antennae like a hand, in order to build these wax walls and bring to the mouth the nectar and pollen collected from flowers.
The use of wax as a thermal isolator proves exceptionally effective in the trample steppe (and also in the coldvanna) during winter when the soil freezes completely. During these harsh months, waxants seal the entrances of their anthills with a wax cap and huddle close to their queen ants for warmth. Occasionally, they generate heat by rapidly rubbing their abdomens against each other, aiding in maintaining a relatively constant temperature inside the ant colony. Thanks to these adaptations, waxants represent the southernmost ant species in Antarctica, even being found in several patches of moss tundra, where they are the main pollinators of this cold and hostile environment.

Other invertebrates have chosen a different approach to stay warm during winter by utilizing the heat from animals, exemplified by a recently diverged group of ectoparasitic insects known as skin insects (Zoococcus spp.). They constitute a highly derived group of scale insects which, rather than using their pointed proboscis to extract sap from plants, prefer to feed on the blood of large mammals and birds. This shift from sap-sipping to a blood-based diet is not a novel occurrence in the insect world, but a common evolutionary eventuality. At least six separate lineages have transitioned to a blood-sucking diet, likely stemming from sap-sucking species.

Like all coccoids, skin insects exhibit significant sexual dimorphism and a predominantly female population. Females are born flightless and, in their final stage, become immobile, remaining firmly attached to their host thanks to special hooks on their bodies. They usually reproduce through parthenogenesis throughout the year, producing small eggs that often become entangled in the fur or feathers of the host and are subsequently dispersed to other individuals through direct contact. Males are infrequent in the life cycle of skin insects, becoming slightly more common (0.01% sex ratio) during winter—a primitive trait of all scale insects aimed at enhancing survival during the food shortages of the harsh season. Despite not experiencing a shortage of food, even in winter, skin insects maintain sexual reproduction to a limited extent, ensuring at least a minimal level of genetic recombination.