At first, you might not notice them, but ants in a woodland are important. Their presence indicates healthy woodland, and the Forestry Commission recognises them as a ‘keystone species’ in the woodland / forest ecosystem and encourages woodland owners to treat them sympathetically.  Ants, like bees and wasps, belong to a group of insects known as the Hymenoptera .  These are insects with membranous wings and narrow ‘waists’. Like bees, ants are ‘social insects’  and within their nests, there is a division of labour (workers, soldiers, queens).    There are four main species of true wood ant - Formica rufa, F. aquilonia, F. lugubris and F. pratensis. Ants are important for a number of reasons, for example :- They help disperse seeds.  They manage pests by preying on herbivorous insects that damage leaves They contribute to nutrient recycling, t Their nests provide a habitat for a whole range of invertebrates that live specifically in wood ant nests. For example, the woodlouse  (Platyarthrus hoffmannseggii), which has ‘lost’ its eyes and colour and is completely adapted to living in the dark recesses of the ants’ nests. They are a source of food for various predators including woodpeckers. Through the building of nests, they affect the soil profile, the drainage and permeability of the top soil, and help with the distribution of various nutrients.  A wood ant colony nest can persist for many years and survives so long as there is a queen / s present.   During the winter months, only queens and a limited number of the workers live on deep inside the nest. Once the temperature begins to rise in the Spring, then workers will begin to emerge and start to forage – and the queen(s) will begin to start laying eggs again.   Fertilised eggs will give rise to female ants, and unfertilized eggs give rise to males.   The males and queens have wings, and are bigger than the workers. The life expectancy of a worker is about 60 days.   Ants such as the southern wood ant [Formica rufa]. build large, ‘thatched’ nests, (see the film link below) which may contain many thousands of workers and queens (up to a quarter of a million). An ant nest is instantly recognisable, it looks like a roughly shaped dome, made from an untidy heap of leaves and twigs – with ant trails leading to and from. The heart of the nest is deep underground, whilst on the surface is the dome shaped ‘thatch’. The thatch consists of a variety materials in the thatch – small twigs, moss, heather, pine needles.   These materials are positioned so that they  not only intercept the sun’s rays to help warm the nest  but also are laid in such a way that water / rain runs away from the nest, reducing the risk of flooding.  Some ant species build their nests in /on gravel or sandy / stony soils - which reduces the risk of water logging. Like many insects, ants make use of pheromones (volatile chemicals). For example, to lay paths to the nest. The study of ant trails and ant behaviour has inspired computer programs / simulations to the “travelling salesman problem”, that is finding the shortest route round a large number of fixed locations (think of the Amazon’s driver’s day!  Woodlands TV has produced another film that focuses on woodland ants.  The film, presented by Giles Pitman, can be seen either on this website or on YouTube https://youtu.be/9wtvwlL2Wzg. Interesting fact : Ants can spray formic acid from their abdomen – when threatened. This smells like vinegar and is thought to be a deterrent to birds or other predators.  

The woodlands blog has previously reported on the damage being wreaked by bark beetles.  These beetles may be small (less than a centimetre in length) but their effects on the western forests of North America has been immense. Some areas have lost 90% of their conifers.   Outbreaks of these beetles have been increasing in size and severity.  Indeed, across Europe, the eurasian bark beetle (Its typographus) has killed millions of conifers. Whilst bark is broadly protective, it can also offer a home to certain insects.  Bark beetles lay their eggs just below the bark so that when the larvae hatch, they can feed on the nutrient-rich living tissue of the cambium and phloem. Consequently, the tree's transport systems begin to fail.  The beetles may also introduce disease-causing fungi and bacteria. Ageing stands of trees coupled with warmer winters, which help the overwintering stage of the insect, have contributed to the spread of bark beetles. .  Conifers, by their nature, are not defenceless.  When a pine tree is cut / wounded, it produces a pale yellow and sticky fluid - RESIN to seal the cut or wound [see above image]. This material helps prevent the entry of pests or pathogens, and can stem water loss. The resin may trap insect invaders as  witnessed by those trapped in time capsules of amber.  Resin is rich in terpenes, these are used in the building of many complex organic molecules and contribute to the make-up of the volatile oils, produced by many plants.  Terpenes are made from units of isoprene, which has the formula C5H8. So the basic formula of a terpene is (C5H8)n, where n is the number of isoprene units that have been joined together.  Terpenes are also readily available in coniferous oils, which contribute to the unique smell of a pine forest or a burning log. [caption id="attachment_40973" align="alignleft" width="300"] Old and dying tree[/caption] These ‘chemical defences’ should trap, poison or deter an insect invader, such as the bark beetle.  But it would seem that bark beetles ‘don’t mind’ these defences. Research suggests that the eurasian bark beetle might have an ally.  Certain fungi (from the genus - Grosmannia) are found in association with these beetles. When the  Grosmannia fungi infect spruce trees they alter the chemical profile the trees, so that infected trees produce different volatile chemicals - ie they smell different.  The bark beetles are able to detect these differences and exploit this ‘breach’ of the trees natural defences.  The unique chemical profile of infected trees and the pheromones produced by the beetles probably help explain the swarming behaviour of the bark beetles.  A heavy beetle infestation results in the death of a tree. However, there is a possible positive in this rather sad tale.  At present, traps for bark beetles rely solely on using pheromones but if the pheromones can be combined with the chemicals produced by the fungi then it opens the door to more effective beetle traps.  

Plants and their ‘predators’ i.e herbivores have been engaged in an “evolutionary arms race” for millions of years. The blog has already explored how thorns, prickles etc act as a defence against larger herbivores.  But what about the caterpillars, aphids that feed upon leaves, bark and other tissues ?  Thinking of plants as just passive organisms would be wrong; they have a number of strategies that can be deployed. Read more...

Plants and animals provide us with many important ecosystem services.   One critical ecosystem service is pollination; this is mainly done by insects - such as bees, bumblebees, moths and hoverflies. Insects are often attracted to flowers by scent, when volatile oils are released that act as chemical signals to ‘tell’ insects about their presence in the environment. This signalling is the result of a relationship between flowers and insects that has evolved over millions of years.  However, in relatively recent times, we (as a species) have been responsible for many changes to the Earth and its atmosphere.  Many gases and materials have been released into the air which have ‘mixed’ with the wide variety of natural scents and smells that are used for plant and animal communication. One such pollutant at low levels is ozone. Higher up in the atmosphere, the ozone layer prevents too much damaging UV light from reaching the Earth's surface.  However, at ground level, the oxidizing potential of ozone can cause damage to respiratory tissues in animals. Read more...

The woodlands blog has previously reported on the havoc being wreaked by bark beetles.  Such beetles may be small (about half a centimetre in length) but their effects on the western forests of North America is colossal - indeed some parts have lost 90% of their conifers.   Outbreaks of these beetles have been increasing in size and severity. The beetles onward march was generally kept in check by long and cold winters, but with warmer temperatures (especially in the winter months) and a longer season for reproduction bark beetle populations have been gaining ground, even making their way into parts of the boreal forest of North America. Read more...