Ecology And Control Of The Highland Midge Biology Essay
This essay intends to sketch the ecology and control of the upland midge Culicoides impunctatus. It will give an overview of the Habitat and life rhythm of the upland midge every bit good as discoursing some of the jobs caused by this species such as effects on touristry and forestry. It will besides discourse the efficaciousness of assorted control methods that may be employed in an effort to command this plague species.Culicoides impunctatus is a member of the household Ceratopogonidae and the insect order Diptera ( true flies ) , is about 1.
4mm long and weighs about 0.5 Aµg. The upland midge can be differentiated from other midge species such as the garden midge ( Culicoides obsoletus ) due to characteristic dark splodges on their membranous wings. Culicoides impunctatus are holometabolic insects, as they go through assorted phases of growing ( known as instars ) , which are separated by molts. Culicoides impunctatus can happen at immense population densenesss in Scotland, e.g. set downing rates of 10-635 midges/min on an open human arm ( Carpenter et al, 2005 ) .
The upland midge ‘s preferable home ground is marshy, acidic dirt, such as quags and the passage zones on the border of bogs. These home grounds are frequently characterised by hastes such as Juncus articulatus and Juncus acutiflorus, every bit good as the presence of Sphagnum spp. , and the violet Moor grass, Molinia caerulea. These workss characterise dirt with adequate H2O content for the development of midge larvae, this home ground is rather common in the North and west Highlandss of Scotland. Culicoides impunctatus usage these countries as genteelness sites, as their larvae are semi aquatic and will submerge in unfastened H2O, but are besides vulnerable to dehydration in dry dirt.
In a suited home ground midge larvae can be found in densenesss of up to 700 per square meter ( SNH )Fig 1 – The typical home ground of Culicoides impunctatus, incorporating peat bog, H2O and shrubbery.Culicoides impunctatus is bivoltine, with 2 coevalss of grownups get downing in early may and widening to late September ( Blackwell et al, 1992 ) The first coevals begins its life rhythm as an egg, which is laid during the summer months in countries of moist dirt, these eggs are by and large laid in batches of 30-100 about 5 yearss after the female is fertilised. The larvae hatch within a twenty-four hours and tunnel into the top bed of dirt. The larvae of Culicoides impunctatus are both omnivores and detritivores ( devouring debris is the dirt ) and feed on other larvae, Protozoa, green algae, and roundworms. Triggered by an addition in temperature and hours of daytime the larvae enters the pupal phase, this stage by and large lasts for 1-2 yearss. Once metabolism has taken topographic point the midge emerges to the full formed and typically has a life span of between 20-30 yearss. The larvae of 2nd coevals females survive over winter by come ining a 4th instar stage, populating as larvae in the dirt ( Blackwell et al, 1992 ) . Larvae of Culicoides impunctatus develop easy when compared to other species in the genus ; this may be due to the alimentary hapless dirt in which they develop ( trees for life ) .
The grownup female upland midge has the ability to put a first batch of eggs without the demand for a blood repast. This is done utilizing alimentary militias built up in the larval phase. This may be one of the grounds for the high Numberss of Culicoides impunctatus in the Highlandss. The grownup female nevertheless carries many more eggs than can be matured utilizing these alimentary militias.
It is merely after the first batch of eggs is laid that the female requires protein from a blood repast to supply the yolk for extra eggs. This bloodsucking behavior is known as haematophagous. This blood repast can be obtained from a big figure of mammals, recent surveies have shown that the intestine of Culicoides impunctatus contained the blood of cowss, cervid, sheep, worlds, cats, Canis familiariss, mice and coneies ( SNH ) . It was besides noted that worlds were non actively preferred over other animate beings, and were merely bitten opportunistically ( Blackwell, Brown, & A ; Mordue, 1995 )Research grounds has shown the grownup female Culicoides impunctatus are attracted to dark colored traveling objects, particularly when these objects are associated with the release of C dioxide ( CO2 ) which is released when mammals exhale. This well developed olfactive sense is besides used to observe other chemicals which are secreted in the organic structure smell of mammals such as propanone and lactic acid ( Mordue, 2003 ) . After turn uping the host the upland midge bites utilizing short blade like lower jaws, these are used to do a shoal lesion, the midge so feeds on the capillary blood from the lesion. After around 5 proceedingss the midge becomes engorged and ceases feeding. Once the grownup female midge has finished eating, she releases a pheromone, which acts to pull other females.
The upland midge is a major plague species in the Highlandss of Scotland, doing terrible irritation to both adult male and farm animal due to their onslaughts, research suggests that Culicoides impunctatus are responsible for around 90 % of bites on worlds. Culicoides impunctatus besides cause major break to outdoor industry and touristry during the summer months ( Hendry and Goodwin, 1988 ) Forestry workers can be peculiarly vulnerable to midge onslaughts due to the fact they frequently work low to land and in shaded countries where Culicoides impunctatus are active throughout the twenty-four hours, it is estimated that up to 20 % of summer working yearss in out-of-door occupations such as forestry are lost due to midge activity ( trees for life ) . Tourism may besides be affected with people being deterred from sing the Scots Highlandss due to high degrees of upland midge activity, or being deterred from returning to the Scots upland on vacation due to the idea of being attacked and bitten by the upland midge ( SNH ) . The Scots touristry industry is estimated to be deserving ?2 billion lbs per annum ( Hendry 1996 ) , the loss of income through visitants non sing or returning to the Highlandss is presently undocumented and can merely be guessed at ( Blackwell & A ; Page, 2003 )For the grounds stated above research is being carried out to happen and implement some sort of control for the big population of Culicoides impunctatus. This essay will now travel onto discuss some of the possible methods of commanding the upland midge.At present no effectual chemical control exists for the control of Culicoides impunctatus.
Spraying of sites would be uneffective as grownup upland midge frequently rest in crannies or the bottoms of foliages. Even if a important Numberss of Culicoides impunctatus could be killed, repeated crop-dusting would be required as more midges emerge throughout the summer months. Control of upland midge larvae is every bit hard. Any insecticidal control used would hold to be relentless plenty to perforate the deep dirt the midge larvae live in.
Persistent insect powder usage would besides take to rapid opposition development. Furthermore the larval home ground is so common in Scotland that the insect powder costs would quickly go prohibitory. This is evidenced by the fact that Culicoides impunctatus was the mark of several unsuccessful insecticidal tests by the section of wellness for Scotland in the 1940 ‘s and 50 ‘s ( Kettle, 1996 ) . The crop-dusting of chemical insect powders is besides extremely non particular and would cut down overall Numberss of insects, including some species which may feed on Culicoides impunctatus. This may really take to an addition in upland midge Numberss.
Due to the complete deficiency of predation, Culicoides impunctatus may go a renascent plague.Biological control agents are presently being investigated, such as the control of larvae by spraying with roundworms, but these steps are likely to hold the same jobs as chemical control methods. The control agents ( roundworms ) would hold to prevail in the midge home ground and besides be cheap plenty to let perennial interventions of a big country of home ground. Inoculative control such as utilizing natural enemies are likely to be unsuccessful as Culicoides impunctatus is a native species and is improbable to hold any natural enemies abroad which do non already be in the Highlandss of Scotland. In add-on to this, although the upland midge is so legion, it is non a major nutrient beginning for any insectivorous animate beings or birds. Bats such as Pipistrellus pipistrellus ‘s ( Pipistrellus pipistellus ) do eat insects such as the midge, but this is a really minor portion of their diet.
Birds such as warblers ( Phylloscopus spp. ) and Swifts ( Apus Apus ) will besides on occasion feed on the upland midge. Midges are besides a nutrient beginning for insectivorous workss such as daily dews ( Drosera spp. ) and butterworts ( Pinguicula vulgaris ) . These workss flourish in the acidic, boggy dirt where midges live, but the Numberss caught by these workss are undistinguished when you consider the immense Numberss of Culicoides impunctatus. The midge larvae are on occasion fed on by the larvae of other dipterous flies, every bit good as the larvae of coleopterous species, but as with the works species, the Numberss consumed are undistinguished. It has been theorised that the big Numberss of Culicoides impunctatus may be due to the deforestation of some countries of the Scots Highlandss.
Deforestation could hold caused increased H2O content in the dirt, making a perfect genteelness land for the upland midge. This theory may besides explicate why no species take advantage of the big Numberss of the upland midge, as deforestation was a late modern development, this would non hold allowed important clip for a specialized midge marauder to germinate. Recent surveies in Skye and Argyll have found that the larvae of 2 species of touchs ( Parafeiderium stuarti & A ; centrotrombidium blackwellae ) are parasitic on the grownup midge ; this research suggests that these larvae could be used to supply a biological control for Culicoides impunctatus.Recently much research has been done to look into the consequence of midge aroma traps on commanding midge Numberss, these have been reasonably successful. Devicess which are known as midge magnets and midge feeders have late been marketed as an effectual control method. As stated earlier Culicoides impunctatus detect hosts to seize with teeth by utilizing their sense of odor to turn up both C dioxide and natural chemicals given off by mammals such as propanone and lactic acid ( Mordue, 2003 ) .
In add-on to this it has been found that the upland midge is attracted to a chemical known as 1-octen-3-ol ( Blackwell et al, 1996 ) ; ( Bhasin, Mordue, L, & A ; Mordue, W, 2000 ) this chemical with the add-on of C dioxide is exhaled by mammals, and therefore is a powerful attractant for midge species. Surveies have shown that Culicoides impunctatus are sensitive to this chemical at a release rate of 0.11 mg/day ( Bhasin, Mordue, L, & A ; Mordue, W, 2000 ) . These midge catching devices give off a mixture of certain chemicals ( 1-octen-3-ol, propanone, lactic acid and CO2 ) , and have the potency to catch 1000s of Culicoides impunctatus per twenty-four hours. It should be noted nevertheless that the arrangement of these traps is of import, traps should be placed to pull midges off from human home grounds instead than towards them, besides the success of these traps improves over clip, catching more midges a few hebdomads after arrangement than within the first few yearss. These midge traps are extremely specific, and hence do non harm any other insect species.Fig 2 – A portable midge magnetDespite ne’er being tested on Culicoides impunctatus, insect growing regulators ( IGRs ) that disrupt metabolism have been shown to be effectual against the larvae of Culicoides sonorensis.
Laboratory surveies in the USA utilizing field collected larvae showed that similin in measures of 0.5 p.p.m were effectual in commanding outgrowth of the midge by 90 % ( Apperson & A ; Yows, 1976 ) . This method may hold some possible to command midge Numberss in the Scots Highlandss.Midge repellants are besides frequently used in an effort to halt Culicoides impunctatus from seize with teething worlds.
Most modern insect repellants contain a chemical called di-ethyl toluamide ( DEET ) , this chemical has been proven extremely effectual in discouraging the upland midge from biting, and is the active ingredient in most of the midge repellants on sale today. DEET nevertheless has been proven to be toxic, and as such should non be used often ( Selim, 1995 ) . Recently nevertheless a midge repellant ( known as shred ) has been developed which interferes with the midge ‘s ability to turn up its quarry by confounding the midge ‘s sense of odor. Smidge is wholly DEET free and harmonizing to makers can be used safely on grownups and kids older than 30 months.
This is nevertheless is a recent development, and as yet no field tests have been carried out. It is hence hard to find the efficaciousness of this repellant.To reason the high population of Culicoides impunctatus is still a job in the North and west Highlandss of Scotland.
However a big sum of research is being conducted with a position to commanding the Numberss of this peculiar plague species. The go oning development of new and improved control methods such as insect growing regulators ( IGRs ) , scent traps such as the midge magnet, and midge repellants such as shred show that advancement is being made in undertaking this job plague.