Presentation on theme: "Introduction to Mosquito Biology and Key North Texas species"— Presentation transcript:
1Introduction to Mosquito Biology and Key North Texas species Notes may be available in some Powerpoints to help clarify individual slides. Note that the information in these slides was developed for north Texas and may not be completely applicable to other parts of the state, or other states.Michael Merchant, PhD, BCEProfessor and Urban EntomologistTexas A&M AgriLife Center at Dallas
2Mosquitoes: Culicidae 3,500 species worldwideOccur on every continent except Antarctica.Most important arthropod affecting human and animal health.Diverse habitats; some have become “domesticated”.Hundreds of millions of dollars spent on control in U.S. for nuisance reasons alone.Courtesy G. Hamer, Dept. Entomology, Texas A&M University
3Anopheles Malaria mosquito 219 million cases in 2010 (cf. 34 m AIDS cases)660,000 deaths annually90% cases in Africa$1.84 b international aidNote that malaria used to be endemic to the US as late as 50 years ago. According to CDC, “The National Malaria Eradication Program, a cooperative undertaking by state and local health agencies of 13 Southeastern states and the CDC, originally proposed by Louis Laval Williams, commenced operations on July 1, It consisted primarily of DDT application to the interior surfaces of rural homes or entire premises in counties where malaria was reported to have been prevalent in recent years. By the end of 1949, over 4,650,000 house spray applications had been made. It also included drainage, removal of mosquito breeding sites, and spraying (occasionally from aircrafts) of insecticides. Total elimination of transmission was slowly achieved. In 1947, 15,000 malaria cases were reported. By 1950, only 2,000 cases were reported. By 1951, malaria was considered eliminated from the United States.” For more info, see
4Recognizing Mosquitoes from Bohart and Washino. Mosquitoes of CaliforniaRecognizing MosquitoesThe fly order (Diptera)Family Culicidaelong proboscislong legsscales on wing veins172 species in U.S.85 species in Texas37 species in Dallas County (DCHHS)Other insects commonly confused with mosquitoes include crane flies, lake midges, and fungus gnats.
5Mosquito life cycle adult pupa eggs larva Typical generation times for mosquitoes last 10 to 14 days or more, starting with adults who feed 1-3 days after emergence on nectar sources. After its first blood meal the mosquito typically rests for 2-5 days for eggs to develop in the ovaries (gestation period). Eggs typically hatch within 48 hours (1-2 days). Larvae go through four instars and typically require 6+ days to reach the pupal form. Under ideal conditions, the pupa stage lasts 2 days.The duration of the egg, larvae and pupae stages depends on temperature and the mosquito species itself. For instance, Culex tarsalis might go through its life cycle in 14 days at 70 F and take only 10 days at 80 F. Also, some species have naturally adapted to go through their entire life cycle in as little as four days or as long as one month.larva
6Culex EggsPhotos: Institute for Clinical Pathology and Medical Research, University of Sydney, Australia
7Aedes eggs US Armed Forces Pest Management Board The pictures show an Aedes oviposition trap consisting of a black cup with tongue depressor wrapped in paper towel. Ae. aegypti and Ae. albopictus lay their eggs on moist surfaces next to shiny water sources like this. Stink water is not needed in Ae. traps, rather the mosquitoes are attracted to the black “hole” and reflections from the water.Ovitrap with eggs of Aedes aegypti
8Marin/Sonoma Mosquito and Vector Control District Mosquito emerging from pupal skin, a process that takes minutes. After this the mosquito is no longer aquatic, but a flying insect. The adult life span is variable but may last 4-30 days.Marin/Sonoma Mosquito and Vector Control District
9Mosquito larvae Aquatic insects 4-14+ days from egg to adult Adults may be strong to weak fliers, depending on speciesPhoto: M. Merchant, Texas A&M AgriLife
10Mosquito mouthparts Modified from Scientific American, Tom Prentiss Mosquitoes have piercing sucking mouthparts. The purple part is the hollow hypopharyx, through which saliva (and if the mosquito is infected, virus particles) flows into the wound. The saliva is the carrying agent for viral pathogens. A mosquito’s ability to catch, replicate and become infective is called vector competence.
11Mosquito feeding Mosquito hosts Plant nectar or honeydew for first 3-5 days after emergenceBlood of vertebrate hosts need for most species to initiate egg developmentBirdsMammalsReptilesAmphibiansDifferent species generally specialise in a particular kind of host, though some mosquitos, like the southern house mosquito, may feed on a variety of hosts, like birds and humans.
13Common pest species in Texas Floodwater speciesPsorophora columbiaeAedes vexansStanding water speciesAedes albopictus/aegyptiAedes solicitansCulex quinquefasciatusCulex tarsalis
14Floodwater species Psorophora spp. Aedes vexans Typically live 4-5 days (up to one month)Excellent fliers (5-10 miles or more)eggs survive up to 2 years in soilpainful bites
15Floodwater species Difficult to control drainage of marshesfloodwater controlcommunity foggingavoidanceWater only needs to stand 3-4 days to successfully breed mosquitoesNot important disease vectorsThe most important thing to remember about floodwater mosquito species is that they are nuisances, but generally not important disease vectors—at least in most parts of Texas.
16Major standing water species Culex, Aedes Culex quinquefasciatusCulex tarsalis (West TX)Our most medically important species
17Culex spp. mosquitoes responsible for WNV human incidence Culex tarsalisCulex pipiensThere are three important vectors of West Nile virus in the US. This map shows their approximate geographical distribution. Note that higher numbers of cases of WNV are seen in rural counties where Culex tarsalis is the key vector. Cu. tarsalis is more agricultural compared to the pipiens/quinquefasciatus complex.Cx. quinquefasciatusSugumaran et al. 2009Dept. Entomology, Texas A&M UniversityCourtesy G. Hamer, Dept. Entomology, Texas A&M University
18Culex quinquefasciatus Southern house mosquito delicate, dull brown mosquito; lacks bands on tarsi and proboscisprefers polluted water in containers or other standing watermostly feeds on birds, but thought to be principal vector of WNV to humansOur principal WNV vector in Texas.
19Other standing water species Aedes albopictus* - Asian tiger mosquitoSince early 1990s in eastern TexasDaytime biterAedes aegypti – yellow fever mosquitocontainer breedervector of yellow fever, dengue feverbeing replaced by tiger mosquito?Aedes solicitans – salt water mosquitosaline/brackish watervicious, daytime biterAe. solicitans is more common along Gulf coast areas in Texas.
21Most common mosquito complaints in Dallas, TX Aedes albopictusReadily bites humansBreeding sites within 1-3 blocks25% complaints can be traced to complainer’s property (Dallas Co. Health & Human Svcs. Dept.)
22Why the difference between Aedes & Culex? Culex resting sites8 – 10 feetAedesAs we will see, behavioral differences between Culex and Aedes affect treatment choices. Which species do you think would be better suited to control via air, versus ground spraying?