Northern Jewelled Spider

Gasteracantha fornicata is a small spider that displays multiple morphs in size and colour. It has exoskeletal spines across its dorsal side. The wide cephalothorax structure of Gasteracantha may prevent it from being as mobile compared to spiders of similar size. Males are typically two millimeters while females grow up to twelve millimeters. Females have distinct stripes across the dorsal region that are known to attract prey. These yellow/white bands starkly contrast with the spider's dark coloured body. Like other orb-weaving spiders the bright colouration of the spider has been shown to help attract prey. On the ventral side, the body is darker and has small yellow spots. Like other spiny spiders, Gasteracantha fornicata has a hard exoskeleton with spines along the dorsal side for predatorial protection. The bright colouration of the spiders have been suggested to signal to predators that they are not ideal prey. Female Gasteracantha fornicata spiders have two different morphs, one with bright yellow bands, and another with white bands (spectral curves at 447 nanometers and 496 nanometers). Although the spider can have white-coloured stripes, it does not possess the same UV properties as the closely related Gasteracanthra cancriformis. Different coloured morphs inhabit different regions of the rainforest habitat with varying frequencies. …

Gasteracantha fornicata originates from the Northeastern Australian rainforest. This spider has been found strictly in the rainforest, specifically at the border of the tree line as a microhabitat. Variations in cloud coverage and sunny clearing within the habitat have been found to impact the colouration frequencies of female spiders. In addition, long periods of rainfall within the region render their webs ineffective.

The diet of Gasteracantha fornicata is largely consistent with that of other spiders in the genus. This includes small dipterans (flies), small hymenopterans (members of the bee family), Orthoptera, Odonata, and Lepidoptera. The range of prey species does not vary with spider colour. Building a web is the main foraging cost of this species. Gasteracantha fornicata orients itself and its web to take advantage of light and dark patches in the vegetation. The light and dark bands mimic the environment and serve to attract prey as a part of the colour-as-prey-attraction hypothesis. These spiders effectively utilize their colouration to have the best web visibility and attractiveness within their habitat. Prey typically mistaken the light patches as forager or mating sites, serving as a strategy for Gasteracantha fornicata. This strategy has varying effects on the capture environment of yellow striped spiders versus the white striped spiders. Yellow striped spiders have been found to have the largest number of prey-capture events when it stood in greatest chromatic contrast with the surrounding area (the yellow stripes stand out the most when compared to other colours in the environment). White striped spiders best capture prey when in achromatic contrast with the surrounding area (the brightness of the white stands out the most when compared to the luminescence of the environment). …