Moruga Bouffe - The Trinidad and Tobago Field Naturalists' Club

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Page 4 THE FIELD NATURALIST Issue No. 2/2011Annoying and Blood Sucking Arthropods of Trinidad and Tobago3. Simulium Black Fliesby Elisha S. Tikasinghelisha.tikasingh@gmail.comBlack flies, Simulium, are sometimes mistakenly called sand flies probably becausethey are small, usually less than 5.0 mm in length. While many members of thisgroup are black, there are others that are grey, yellow or orange. The antennaeand legs of a black fly are short, the thorax is somewhat arched giving it ahump-backed look, and their wings are clear.These black flies are called buffalo gnats in theU.S.,cabouri or kabowra flies in Guyana, pium inBrazil and congo flies in Trinidad. Their bites arevery painful and very more so than the sand flies.This is due to their mouth parts which containblade-like lancets which macerate the skin at thebite site causing intense pain. The saliva introducedin the bites cause an allergic reaction with severeitching and swelling. )Simulium Black Flyfeeding on human armPhoto: Elisha TikasinghEffects of Black Fly bites.Initial bite may be accompanied by a red spot(shown in circles) and later by local swelling.Photo: Elisha TikasinghBlack flies breed in fast running streams, creeks and riverswhere the water is well aerated. They will not breed inponds and stagnant water. Eggs are deposited in massesnear rocks, aquatic vegetation and other objects in thewater which the larvae cling to on hatching.(Continued on page 4 )Back Fly larva on vegetation.Next to it is an empty pupal skinPhoto: Elisha Tikasingh
Page 5 THE FIELD NATURALIST Issue No. 2/2011(Continued from page 3)The larvae undergo six moults and then spins acocoon for pupal development. The pupa containsmany filaments which are very diagnostic to thespecies level.Staff of the Trinidad Regional Virus Laboratory havecollected and identified seven species mainly fromthe rivers of the Northern Range (CAREC unpublisheddata). Based mainly on adult morphology thefollowing species were: Simulium clarki, S. metallicum,S. placidum, S. incrustatum, S. sp. near incrustatum, S.samboni and S. subnigrum).In Trinidad and Tobago, black flies are not known tocarry any disease, but elsewhere such as northAmerica in the spring and summer months theyemerge in such large numbers that they annoyanimals preventing them from feeding resulting inemaciation and sometimes they may even enter thenostrils of the animals suffocating them causing theirdeaths. In Guyana, they also emerge in largenumbers during the rainy season so that people arereluctant to go in the interior and thus preventingdevelopment of the area.Back Fly cocoon stageimage found at:ttp://www.bgsd.k12.wa.us/hml/jr_cam/macros/upper_efl_f05/up_efl_f05a.htmlThe adults are difficult to identify and generally onemust have the associated pupal skin for definitiveidentification. The next time you are at a mountainstream where the water is not polluted, check theleaves of vegetation or sticks submerged in thewater and you may find black fly larvae and pupae.The entire life cycle from egg to adult may take fromtwo to three months depending on temperature theof the water. Black flies are very robust and arestrong flyers and may be found far from theirbreeding sites. Adults are active during the day, andhardly enter homes.In West Africa, Central America and Venezuelaspecies of Simulium carry a threadlike filarial worm,Onchocerca volvulus to people living near rivers. Theadult worm live in subcutaneous nodules on thejoints or trunk (Africa) and shoulders and head(Central America and Venezuela) from where theyproduce larvae called microfilariae which arereleased to other parts of the body. Some of themicrofilariae may enter the eye causing blindnessand the disease known as ―river blindness‖ oronchocerciasis. When one sees pictures showing―the blind leading the blind‖ the blindness in theseindividuals is usually due to onchocerciasis.In Guyana and the Brazilian Amazon, Simuliumspecies of the amazonicum group (now identified asS. oyapockense) are vectors of the filarial wormMansonella ozzardi to humans (Nathan et al. 1982,Shelley et al. 1980, Shelley et al. 2004). Infection withMansonella ozzardi may cause articular painparticularly in adults.Control is by killing the larvae at its breeding sites.Fogging with an appropriate insecticide givetemporary relief. Personal protection is by the useof insect repellents.(Continued on page 12)
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Moruga Bouffe - The Trinidad and Tobago Field Naturalists' Club

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