This blog is part of our colourful countdown to the holiday season where we’re celebrating the diversity and beauty of the natural world. Click here to read the rest of the colour countdown series.

Dani Davis of Florida State University sheds light on the story behind her winning Capturing Ecology award photograph, and the complex and mysterious abilities of spider that acts like a cat.

Animals that can change their colour never cease to amaze; from dazzling cuttlefish to disappearing chameleons, these creatures captivate our interest. However, these more well-known species may be welcoming a new member to the colour-changing club, an emerald-green spider known as the green lynx (Peucetia viridans). Green lynx spiders seem to share in the ability to camouflage into their background by matching the colour of the flower on which they sit and wait to catch prey, but how and when these spiders change their colours is not well understood.

Late summer is a captivating time to walk through the forest in the green lynx’s native range, stretching across the southern United States and into Mexico. Plants are particularly stunning at this time; tall inflorescences shoot up to attract visitors, bright green leaves of pitcher plants abound, and a sea of yellows, white, and purples dot the landscape. It’s during this time of year when the green lynx spider is most apparent. The spiders are up high on vegetation, feeding on the pollinators that are actively visiting during this time. Looking around at spiders on different plant species, one begins to notice something strange. It appears that the adult spiders are blending into their plant backgrounds by changing their body colours.

Finding adult spiders in the field during summer is surprisingly easy. To us humans, the spiders are quite conspicuous. Their propensity to sit at the tops of plants, either holding tightly to flowering spikes, often hanging upside down, or nestled among the flower tops, makes them easy to spot. Deriving their common name from their hunting style, the green lynx is an active hunter, either pouncing on pollinators or chasing down a host of general insects that happen to cross the spider’s path. When the unlucky insect attracts the green lynx’s attention, the spider pounces on its prey, quickly injecting it with a potent venom capable of subduing large and cumbersome prey.

The spiders all share the same green body with little white chevrons running down their backs, but many have slightly different colours expressed on the sides and top of their abdomens. Their voracious appetite and the ability to change colour to match their plant background would be helpful for them to either hide from predators or their prey. This ability has been noted in natural history observations and the spider literature but has not been well studied and is far from being understood.

The ability to change colour is relatively rare in spiders. It has been noted that some orb weavers and at least six species of crab spiders may change their colour in response to their flower background. The green lynx could add another species to this small list of colour-changing spiders, but more work is needed to confirm this. A study from Robertson et al. (1994) noted that pregnant green lynx spiders might change their colour to match green, purple, and white background over 16 days. But very little is known about the how the spiders shift from their basic green and white colours to match the complex colour patterns found in flowers.

In research conducted at Florida State University under the direction of Dr. Tom Miller, we have been investigating to what extent there is colour variation in the green lynx, along with its ability to colour change with both observational and manipulative studies in the lab. First off, we need to assess whether green lynx spiders match their flower backgrounds in the field, we collected 38 spiders from the Apalachicola National Forest in Florida. These spiders were collected from three distinct colour backgrounds: purple flowers (Liatris spicata), white flowers (Eupatorium altissimum), and bright green leaves (Sarracenia flava), taken back to the lab, and photographed.

To get an accurate representation of the spiders’ colouration, we used a new method – the Colormesh pipeline – which begins by standardising the spider abdomens’ shapes using the geometric morphometrics software TPS Series. The software works by contouring all of the spider’s bodies to be the same shape through the placing of landmarks on the image around the abdomen. Then, each image is fit with an array of 1515 triangles that covered the body of the spider and measured for red, green, and blue colour values. These data are then used to investigate the specific, complex colour patterns for individual spiders and to correlate these patterns with the plant background on which the spider was found.

The results from the colour analysis show that there is significant variation in the green colouration, specifically between spiders collected on different backgrounds. Colour differs between spiders, primarily around the chevrons running down the spider’s abdomen, where the presence or absence of green colouration was noted. From this study of colour matching in the field, it is clear that the background flower colour affects the colour of the spider’s abdomen.

What is less clear, however, is how and when these spiders change their colour. We therefore wanted to see if spiders taken from a plant of one colour (purple, white, or green) could then change their colour to match a new background colour (purple, white, or green). Spiders were again collected from the Apalachicola National Forest and taken back to the lab. This was a full reciprocal experiment, with replicate spiders from each original background being placed into both their original and all possible novel backgrounds. These experimental spiders were then photographed at two weeks and four weeks to explore whether colour change occurred. The results from this study are still being explored and will hopefully shed more light on the potential ability of the green lynx to change their colour in response to the plant on which they sit.         

The mystery of the green lynx’s cryptic colour-changing ability is far from solved. Though it has been shown that there is a definite difference between spider colouration on different plants in the field, mysteries still abound. It is still unknown how the spiders change their colour, what triggers may be associated with this, and whether this is an ability they can use to switch between different plants. The ecological implications are another area of interest in the natural communities where this spider thrives. The green lynx is a voracious predator of pollinators on the plants where they sit and wait for prey, so this camouflage ability of the lynx could negatively affect the plant if the spider a significant number of its pollinators.

It is still unknown whether the green lynx will be known as another species that can actively change their colour in a way that allows it to move from flower to flower. There is still plenty to be learned about this species and what their colourful appearances mean for their ecology and for the plants, pollinators, and predators in their communities. They’re a beautiful species with many secrets left to explore.