This is the second post in a six part blog series about rare insects in the Cairngorms. A new project launched this year to save six endangered invertebrates in the north of Scotland and project officer Gabrielle Flinn will take a closer look at one of these species each month. This time, it's the turn of the shining guest ant - a six-legged jewel. The Rare Invertebrates in the Cairngorms project is a partnership involving RSPB Scotland, the Cairngorms National Park Authority (CNPA), Buglife Scotland, Butterfly Conservation Scotland and Scottish Natural Heritage (SNH).

Smaller shining guest ant (R) sits next to its wood ant host (L)

Famed for its minute size and extra shiny coat the shining guest (Formicoxenus nitidulus) is a real gem to behold, particularly when you spot one in amongst a group of larger, acid-spraying wood ants - which the former treats as its 'hosts'. 

The shining guest ant is special for more than just its appearance; this particular ant chooses to live within the thriving, busy and potentially dangerous environment of wood ant nests. So why choose to live in a wood ant nest? There are a number of reasons the species could have evolved this strategy.

Firstly, wood ant nests are very warm places that maintain an average temperature somewhere between 25 and 30°C during their 'active season'.This is achieved by the ingenious thatched roof structure of the nest, which captures sunlight like a solar panel, keeping the inside nice and toasty.

Secondly, the wood ants provide a feisty and steady defence, spraying formic acid at enemies and coordinating attacks on intruders using alarm pheromones to communicate. Finally, the wood ants also bring in a continuous supply of food, including honeydew from the aphids they farm on pine trees and invertebrate prey that they manage to hunt.

There is clearly a huge advantage to living in wood ant nests, so much so, that over 100 other invertebrate species, including everything from specialised wood lice to cleverly disguised spiders, have been found living inside nests of this type. 

It is a risky game, living in a nest full of easily enraged and well equipped flatmates, so ‘guests’ must be well prepared to survive. This can be achieved by a variety of means including imitating the ‘colony smell’ or simply by being agile and elusive.

The shining guest ant, however has evolved a slightly different strategy. It produces a distasteful substance on its body so that when a wood ant worker investigates its presence and picks it up in its jaws, the wood ant is quick to release it again. This adaptation has proven so effective that several shining guest ant colonies can often be found living in a single wood ant nest at any one time.

Other than what we've already outlined here, very little else is known about this ant species, least of all its distribution across the Cairngorms and the rest of the UK. This is mostly due to the fact that they live within deadwood or bracken inside nests which makes them hard to observe.

However, during the months of July through to November, in ideal conditions, these minute guests can be observed shining on the surface of nests and with some patience it can be rewarding to spot them amongst the busy wood ants. We look forward to heading out with volunteers this summer and autumn to try and spot this sparkling yet elusive ant.

The shining guest ant is a priority species and where wood ants are at risk, this species will experience a knock on effect. Wood ant nests are threatened by loss of woodland habitat, loss of woodland diversity (they love bright glades where they can access the sun!), climate change and various other pressures.

Through the Rare Invertebrates in the Cairngorms project we hope to better understand this species and gather more information about its distribution within the national park. The more we know, the more we can help land owners and managers to protect it.

To read our first blog post in this series, which focused on the Kentish glory moth, click here.You can also follow the Rare Invertebrates in the Cairngorms project on Facebook and Twitter or sign up to our volunteer mailing list by contacting gabrielleflinn@rspb.org.uk

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