DALS WILDLIFE SITE { WILDLIFE OF NORTHERN ENGLAND}

WILDLIFE OF NORTHERN ENGLAND

Hoverflies interesting creatures

Have you ever been panicked by wasp like creatures swarming around ivy flowers, indeed, so many may be present that the whole shrub seems to be alive with movement. Closer observation will reveal that, although the odd wasp may be among the throng, 99% of these flying acrobats will be hoverflies. Unlike the wasp these flies are harmless to humans, and, unlike other flies they are seldom found indoors.

The adults feed mainly on nectar and pollen of open flower species. If they are observed apparently eating foliage , it is more likely that they are drinking honeydew caused by aphids. Many species regard their home as being woodland  but have adapted well  to man made habitat such as parks and gardens.

Hoverflies come in various sizes and have a diverse range of markings. 

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Spring and summer

Hoverflies may be encountered at any time of the year from early spring until late autumn. rarer species may be observed on the wing early spring or early summer, however most of the commoner species take to the wing during July and August here in the north of England.

Gardeners can consider the larvae of hoverflies as an ally, for many species produce larvae that feed on aphids. {greenfly} They may be located in a diverse range of habitat. A search beneath fallen leaves and other vegetation during winter may well reveal these creatures in their larval form. These specimens will be over wintering species.

 

Hoverflies vary in size and colour and like to visit open flowers such as this poppy.

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Species of hoverfly information

Around 250 species of hoverfly have been recorded in Britain. However, some of these are very rare and some are only encountered in specialised habitat. In common with many other species of Invertebrates few have common names and are universally recognized universally by their Latin titles, also referred to as their scientific names.

Common species can be identified by their colour patterning, but these can be variable with darker forms of many species not uncommon. The only positive way of identifying many of the species is by capturing them and to have specialised equipment  such as binocular microscope and other technical instruments  employed by Entomologist. For the layman the colour and patterning may suffice to recognise the common species.

Telling the sexes.

The eyes of most male hoverfies touch at the top. The eyes of most female hoverflies  are seperated as this simple drawing demonstrates

Hoverfly larvae

Having fed and mated and egg development is complete the female will find a suitable location to deposit them. This may be in a variety of locations depending on the species. Some species are attracted to the smell of dung and cow pats. The eggs are placed there and the larvae feed on the dung when it hatches. Others are attracted to aphid honeydew and lay their eggs on plants infested by aphids. The larvae then feed on these creatures.

The eggs can be laid singly or in batches. generally the species whose larvae feed on aphids lay eggs singly or in groups of twos and threes. Those that lay their eggs in water may lay batches of 200 or more. Depending on temperature and humidity the eggs can hatch within 5 days. The higher the temperature and humidity the quicker the eggs hatch. There are generally four types of larvae. Those that feed on plant tissue or sap, Species that scavenge on or filter decaying matter {usually in water}, species that live in nests of social insects such as bees and wasps or ants and those previously mentioned that feed on aphids.

During the day the larvae which feed on aphids tend to be sluggish showing little signs of their effectiveness destroying these creatures. It is at night that they become much more alert and at this time they tend to feed on them constantly. The larvae themselves are also victims of predation.

The species Syrphus ribesii may be encountered on trees, shrubs and herbs where they feed on aphids. There are approximately 20 species in the U.K. that feed on aphids.

The species Neoascia tenur feed in decaying Typha {bullrush}

The species N. podagaria filter manure silage and decaying matter amongst it.

The larvae of Eristalis feed vis filtered water in drains, stagnant water , sewage and polluted water.

 The larvae of the species Myiatropa florea reed in the rot holes of trees especially birch.

The above are just a small selection of the many species and how they feed.

In common with other invertebrate larvae they have skin which is shed during differing stages of their development.  This shedding is undertaken at three stages of their growth which are known as instars. Some species have larvae that reach the third instar then over winter, to pupate the following spring many others do not. Some species may only spend about ten days in the larval stage.

Many species pupate just below the soil surface. others choose the lower surface leave,.leaf litter  or other sheltered places. The larva skin of the third instar is not shed but hardens to enclose the pupae.

Top- some hoverflies imitate wasps, while others imitate the honey bee -below. Note the eyes touch on the hoverfly in the top image indicating a male, while the eyes in the image below are separated indicating a female.

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First to emerge

Males are usually the first to emerge being slightly smaller than the females their development takes slightly less time.

Hoverflies have many enemies. Some fall victim to other insects although this is relatively uncommon. There are solitary wasps that prey on hoverflies along with spiders social wasps and larger flies. They also fall victim to birds especially flycatchers, swifts and swallows.

Hoverflies can be observed in gardens especially where members of the Asteracea {daisy family} are in bloom, and as previously mentioned during September and October when they are attracted to the flowers produced by ivy. 

Top ivy flowers attract hoverflies. Below--In woodland they may be found on foliage such as the one on this oak leaf.             Pics by Dal.Dal

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