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Introduction to Mosquito Biology and Key North Texas species

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1 Introduction 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, BCE Professor and Urban Entomologist Texas A&M AgriLife Center at Dallas

2 Mosquitoes: Culicidae
3,500 species worldwide Occur 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

3 Anopheles Malaria mosquito
219 million cases in 2010 (cf. 34 m AIDS cases) 660,000 deaths annually 90% cases in Africa $1.84 b international aid Note 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

4 Recognizing Mosquitoes
from Bohart and Washino. Mosquitoes of California Recognizing Mosquitoes The fly order (Diptera) Family Culicidae long proboscis long legs scales on wing veins 172 species in U.S. 85 species in Texas 37 species in Dallas County (DCHHS) Other insects commonly confused with mosquitoes include crane flies, lake midges, and fungus gnats.

5 Mosquito 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

6 Culex Eggs Photos: Institute for Clinical Pathology and Medical Research, University of Sydney, Australia

7 Aedes 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

8 Marin/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

9 Mosquito larvae Aquatic insects 4-14+ days from egg to adult
Adults may be strong to weak fliers, depending on species Photo: M. Merchant, Texas A&M AgriLife

10 Mosquito 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.

11 Mosquito feeding Mosquito hosts
Plant nectar or honeydew for first 3-5 days after emergence Blood of vertebrate hosts need for most species to initiate egg development Birds Mammals Reptiles Amphibians Different 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.

12 Mosquito diversity Two basic types Floodwater mosquitoes
Standing water (container) breeders natural sites artificial sites © Boris Krylov

13 Common pest species in Texas
Floodwater species Psorophora columbiae Aedes vexans Standing water species Aedes albopictus/aegypti Aedes solicitans Culex quinquefasciatus Culex tarsalis

14 Floodwater 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 soil painful bites

15 Floodwater species Difficult to control
drainage of marshes floodwater control community fogging avoidance Water only needs to stand 3-4 days to successfully breed mosquitoes Not important disease vectors The 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.

16 Major standing water species Culex, Aedes
Culex quinquefasciatus Culex tarsalis (West TX) Our most medically important species

17 Culex spp. mosquitoes responsible for WNV human incidence
Culex tarsalis Culex pipiens There 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. quinquefasciatus Sugumaran et al. 2009 Dept. Entomology, Texas A&M University Courtesy G. Hamer, Dept. Entomology, Texas A&M University

18 Culex quinquefasciatus Southern house mosquito
delicate, dull brown mosquito; lacks bands on tarsi and proboscis prefers polluted water in containers or other standing water mostly feeds on birds, but thought to be principal vector of WNV to humans Our principal WNV vector in Texas.

19 Other standing water species
Aedes albopictus* - Asian tiger mosquito Since early 1990s in eastern Texas Daytime biter Aedes aegypti – yellow fever mosquito container breeder vector of yellow fever, dengue fever being replaced by tiger mosquito? Aedes solicitans – salt water mosquito saline/brackish water vicious, daytime biter Ae. solicitans is more common along Gulf coast areas in Texas.

20 Aedes albopictus Asian tiger mosquito

21 Most common mosquito complaints in Dallas, TX
Aedes albopictus Readily bites humans Breeding sites within 1-3 blocks 25% complaints can be traced to complainer’s property (Dallas Co. Health & Human Svcs. Dept.)

22 Why the difference between Aedes & Culex?
Culex resting sites 8 – 10 feet Aedes As 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?

23 Questions?

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