Blog - nectar
Where do butterflies come from?
An obvious answer to this question would be - caterpillars. But when did butterflies first appear? There are now some 160,000 species of moths and butterflies -worldwide. Seemingly, they appeared some 100 million years ago - in North America. They evolved from nocturnal moths in the period when flowering plants were undergoing a major expansion (in the Cretaceous period). Butterflies may have become diurnal to avoid predation by bats, or it may have been to take advantage of nectar production and availability [using the proboscis]. The butterflies and their caterpillars were able exploit the diverse range of food resources that these ‘new’ plants offered. Butterflies moved out from North America to South America and then on to other parts of the world, though they probably did not arrive in Europe until some 17 million years ago. The evolutionary expansion of the butterflies has been investigated by researchers at the University of Florida; they analysed the genetic makeup of many species (from 90 countries). They were able to build up a picture of the relationships between the various groups of butterflies and also determined their evolutionary point of origin. They also catalogued the plants eaten by the caterpillars and it was found that some two thirds of butterfly caterpillars feed on plants from the legume family (the Fabaceae - peas and beans). It is probable that the first butterfly caterpillars also fed on these plants. Research at the Georgetown University in Washington DC suggests that larger species of butterfly are ‘coping’ better with higher temperatures, associated with global warming. Bigger wings seem to offer a greater range of movement and the opportunity to find new and suitable habitats. Smaller butterflies are not faring so well. The study involved an analysis of the range of some 90 North American species between 1970 and 2010, during which period the monthly minimum temperature increased by 1.5oF. Others have analysed the butterfly collections at the Natural History Museum, using digital technology. The Natural History Museum’s British and Irish butterfly (and moth) collection is probably the oldest, largest, and most diverse of its kind in the world; some of the specimens date back over a hundred years The measurements of the various specimens were paired with the temperature that the species would have experienced in its caterpillar stage. It was found that for several species that the adult butterfly size increased as the temperature increased (during late larval stage). So, it may be that we will see a gradual increase in butterfly size as temperatures increase with global warming. Join the Big Butterfly Count ? Between Friday 14th July and Sunday 6th August , the big butterfly count will take place. For full details visit : https://bigbutterflycount.butterfly-conservation.org/about Thanks to Angus for images.
Bumblebee pollen collecting
Bumblebees (and bees) collect nectar and pollen. Pollen is a vital food, used in the various stages of a bumblebee’s life. In Spring, newly emerged queens feed on pollen, then it is used to feed its their sister workers. The workers, in turn, take over the feeding of the colony (the larvae and future queens). If not enough pollen is collected, then the colony will not thrive, which can have significant long term effects. Bumblebees are already facing many threats (from habitat fragmentation, agrochemicals and disease). The collection of pollen is a demanding process, and bumblebees will forage over a wide area. They start their pollen collecting activities earlier than many insects as they can warm themselves up by ‘shivering’, that is, rapid muscle contractions which generate heat, warming the insects up ready for flight. Bumblebees can fly in colder conditions and at higher elevations than many other insects. However, research at North Carolina State University has shown that the North American bumblebee (Bombus impatiens) can overheat when exposed to high temperatures (circa 42oC plus). So, if a bee is carrying a significant load of pollen and it is a hot day, its muscles have to work harder and the bee is at risk of overheating. A bumblebee loaded with pollen may be 2oC hotter than an unladen bee; it may be reaching its ‘thermal limit’ - a temperature at which its organs are damaged. Climate change means that many parts of the world are now experiencing extreme weather events, when temperatures can reach into the forties. [caption id="attachment_39978" align="aligncenter" width="675"] Bumblee leaving foxglove[/caption] Increasing temperatures could affect the foraging activities of bumblebees in a significant way - affecting how much pollen is collected and how much pollination takes place. If pollen collection is reduced then colony development is affected and so population numbers will be affected. Bumblebees are key pollinators in natural and agricultural systems, and if their numbers decline there will be ecological and agricultural consequences.
Problems for bees and bumblebees.
The decline in many insect populations across the globe is worrying, threatening economies and ecosystems. A German study in 2017 indicated that the mass of flying insects (in various natural areas) had fallen by some 70%+. The decline in insect populations has been associated with habitat fragmentation, the spread of agriculture and the use of pesticides, with the neonicotinoids being particularly associated with damage to bee and bumblebee populations. Recent work at the University of Konstanz suggests that when bumblebee colonies are exposed to limited resources of nectar and exposure to the herbicide - glyphosate, then their colonies may fail. Bumblebee colonies need a good supply of nectar as a ‘fuel’ in order to maintain a constant brood temperature (of approximately 32oC). Only at this sort of temperature does the eggs & larvae develop quickly from egg to adult, and the colony grow from a single queen to several hundred bees. If the temperature is not maintained, then the brood develops slowly or not at all. The loss of wild flowers (and their nectar) plus the use of the herbicide (in agricultural areas) looks to be a problem for the bumblebees. Just as bumblebees are facing problems, so are honey bees. The bees have faced infections with a variety of viruses, such as the deformed wing virus. This virus affects wing development so that the wings are 'stubby' and useless, plus they may be deformities of the abdomen and leg paralysis; the insect cannot function and dies. The virus is transmitted by the Varroa mite - a parasite (that also feeds on the bees’ tissues). The virus was originally identified in Japan in 1980’s and is referred to as DWV-A. However, a new form of the virus (DWV-B) was identified in the Netherlands in 2001 and it is spreading across Europe, and to other continents. Sadly, this variant of the virus kills bees faster and is more easily transmitted (according to research at the Martin Luther University).
The plight of the bumblebee
We know that insects (especially, bumblebees, bees, hover flies) are the world’s top pollinators, and we also know from many reports that many insect species are in decline. Crops such as tomatoes, blueberries, peppers, cocoa, coffee, almonds and cherries are dependent on these pollinators. Climate change, increasing temperatures and extreme weather events are affecting plants and animals across the world, and it seems that social insects, like bumblebees, are particularly impacted. Research with bumblebee colonies (at Stockholm University) has indicated that if the colonies are exposed to higher temperatures (than normal) then the workers in the colonies were smaller. This decrease in body size could affect their foraging behaviour and the collection of pollen, which would mean less food brought back to the colony and reduced pollination of plants. Studies in the United States looked at some 20,000 bees (bumblebees, leafcutter bees, mason bees etc) along the Rocky Mountains, a region which is vulnerable to climate change. It was found that the larger bees (particularly bumblebees) and those that built nests with combs were affected most by increases in temperature. On the plus side, smaller (soil nesting) bees fared better. Bumblebees would seem to have a lower heat tolerance. The loss of bigger bees, which generally can fly and forage further may again mean reduction in long distance pollination (which promotes outbreeding in plant populations). One reason why hot or hotter weather affects bumblebees is that it influences the nectar that the bumblebees collect. The balance of the various micro-organisms (bacteria and yeasts) in the nectar changes. Whilst bumblebees are attracted to nectar with some microbes in it, a small change in temperature can speed up the metabolism / growth of the microbes so that they use up more of the sugar - with the result that it is less palatable / less nutritious for the bees. Experiments conducted at the University of California have shown that bees did not ‘like’ the nectar rich in microbes, nor a sterile one - with no microbes at all. There seems to be a 'happy medium' in terms of the composition of the nectar. There seems to be a growing consensus that climate change, increasing temperatures and extreme events are pushing bumblebees (in particular) beyond their physiological limits. [caption id="attachment_38081" align="aligncenter" width="650"] Bumblebee visiting foxglove[/caption]
Heat, bumblebees and foraging
Silwood Park is part of Imperial College, a postgraduate campus, located some 25 miles west of central London, near Ascot. It is a centre for research and teaching in ecology and allied disciplines. The campus includes areas of wet woodlands, acid grasslands, traditional orchards and parkland. The veteran and ancient trees support an significant number of rare species of insects, lichens and fungi that depend on decaying wood. Silwood is the heart of the wildlife corridors for the surrounding area. Read more...
Bumblebees need a caffeine fix!
The appearance of bumblebees is one of the hallmarks of Spring, and their buzzing can be heard in gardens throughout the summer months. They are important pollinators in our gardens, but also for some crop species that use buzz pollination (like tomatoes). Like other bees, indeed insects in general, bumblebees face a number of threats - one of which is a fungal parasite (Nosema bombi). This fungus reduces the lifespan of worker bees in the bumblebee colonies and also the production of new queens; it has been associated with the decline in population numbers of North American bumblebees. Read more...
The bees’ search for nectar
Using DNA technology and samples of honey from many different hives, scientists have been able to analyse the foraging behaviour of honey bees, and compare their findings with a study undertaken in the mid twentieth century. In the earlier study, honey samples were analysed by looking at the pollen grains present. The shape and sculpting on a pollen grain is unique for each species. Back in the 1950s, honeybees gathered a lot of pollen and nectar from wild flowers, particularly plants like white clover (Trifolium repens). As with so many wild flowers, there is far less white clover to be found in hedgerows, meadows and roadsides nowadays, so honeybees have to find alternatives - though white clover is a favourite if it can be found. Read more...
Friend or foe ?
Honey bees face many threats - such viruses, mites and pesticides, but also threats from their own kind - robber bees. When nectar becomes scarce at the end of the summer and into autumn, then bees will seek food wherever they can find it - like honey from other colonies. From the robber bees ‘point of view’, this is simply another form of foraging behaviour. This robbing of honey deprives a colony of an important winter resource. To limit this behaviour, hives have guard or gatekeeper bees, who ‘inspect’ all arriving bees. But how do they know who is friend and who is foe? Not being able to tell the difference could mean a long and lean winter, with little honey in the hive. Honey bees can recognise members of their community / hive by detecting waxy chemicals present in their exoskeleton (cuticle) known as cuticular hydrocarbons (CHC’s). Read more...