Riparian Mosquitoes in North Carolina and Virginia. Bruce A. Harrison, Ph.D. Clemmons, NC

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1 Riparian Mosquitoes in North Carolina and Virginia Bruce A. Harrison, Ph.D. Clemmons, NC

2 The word riparian is an ecological term derived from the Latin word ripa, meaning river bank. A riparian zone is the land between the normal banks and the flood stage banks on either side of the main channel of a river or stream. For our use a riparian species is one that most commonly occurs in a narrow to wide zone beside streams, creeks, and rivers, in temporary pool habitats that are created by heavy rainfall and/or flooding from upstream water.

3 Different types of Riparian Zones

4 Spring flood pool off Muddy Creek, Davie County

5 The primary riparian species in NC and VA Aedes cinereus Oc. trivittatus Ae. vexans Psorophora ciliata Ochlerotatus atlanticus Ps. ferox Oc. fulvus pallens Ps. horrida Oc. infirmatus Ps. howardii Oc. sticticus Ps. mathesoni Oc. tormentor

6 What are the main characteristics of immature stages of riparian species? They occupy temporary ground water that is turbid or clear, not highly organic, and only lasts a few weeks. Eggs are deposited on soil, vegetation, leaves, sticks, roots that are periodically inundated by flood waters or heavy rains. Eggs nearly always hatch simultaneously. Typically they develop rapidly from egg to adult in about 5 9 days in new temporary pools and thus, avoid predators. They usually occur in shaded pools. Certain species are commonly found together.

7 What are the main characteristics of adults of riparian species? They usually eclose (emerge) as adults simultaneously. Most species stay in the shade, but will venture out into sunlight if a blood source is nearby. Most species do not fly long distances, but at least one species, Ae. vexans, is known to disperse for miles in association with low pressure systems. They will bite all day in the shade, but prefer dusk and the first couple of hours after dark. Nearly all are vicious mammal feeders and some are enzootic vectors of animal pathogens, while other can serve as secondary vectors of human pathogens. Females oviposit desiccation resistant eggs that can survive for years (up to 8 years for Oc. sticticus).

8 Medical significance of riparian species for humans 11 of 13 species reported positive for WNV by CDC 4 of 13 species positive for EEE virus 3 of 13 species positive for CV virus 3 of 13 species positive for LAC virus 2 of 13 species positive for TVT virus None of the species are considered primary vectors for the above viruses, except for Oc. trivittatus and TVT virus. Their public health importance rests in the huge numbers that eclose simultaneously and are a severe nuisance/impairment to humans that have to be outside.

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10 Aedes vexans M. Cutwa Francis FMEL

11 Aedes vexans hind tarsi narrow hindtarsal bands M. Cutwa Francis FMEL

12 Ochlerotatus atlanticus First Character. Dark scales behind the eyes reach the eyes on both sides. In other words, the eyes are not separated by pale scales from the dark patches on each side of the head. (99 % character) Jung Kim

13 Ochlerotatus atlanticus Second Character. width of median stripe on scutum remains about the same back to the prescutellar area (90-95% character) [This character was found by Roberts and Scanlon 1975] Jung Kim

14 Ochlerotatus tormentor First Character. Dark scales behind eyes do not reach the eyes. In other words, white ocular scales separate the eyes and dark scale patches on the head. (99 % character) Jung Kim

15 Ochlerotatus tormentor Second Character. Width of median line on scutum narrows posteriorly just before it reaches the prescutellar area. (90-95 % character, but variable) Extreme Variation Normal Jung Kim Jung Kim

16 Ochlerotatus fulvus pallens Photos by M. Cutwa Francis FMEL

17 Ochlerotatus infirmatus NOTE. Pale scales on scutum can be white or yellow, and pale area ends before prescutellar area. Jung Kim

18 Banded Ochlerotatus Robert Collins, NCMVCA Oc. fulvus pallens Oc. atlanticus Oc. tormentor Oc. infirmatus Sketches adapted from Bickley and Harrison (Mosquito Systematics, Vol 21 (3) 1989)

19 Psorophora ciliata Black erect scales on Hindtibia and hindtarsomere 1 1. Giant mosquito 2. Adult females bite humans Median longitudinal gold line on scutum 3. Larvae are predaceous on other mosquito larvae

20 Psorophora ferox M. Cutwa-Francis FMEL M. Cutwa-Francis, FMEL M. Cutwa-Francis, FMEL

21 Seasonality of the most common nuisance pests coming from riparian habitats in Brunswick Co., North Carolina

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23 Seasonality (continued) Other riparian species like Ae. cinereus, Ochlerotatus sticticus and Oc. trivittatus occur primarily in the piedmont and mountains and may only appear once each year for a short period after heavy rains in the spring or early summer.

24 Be prepared for these species - ID and map their habitats in your area. - Know the times of the year when temporary water is likely to be in those habitats. - Apply residual larvicides to their habitats just prior to or larvicides of choice immediately after heavy rainfall periods. - Anticipate increased mosquito complaints. - Get your spray trucks ready and monitor daily to determine when eclosion of adults will occur. - Advise residents to use repellents.

25 Why be prepared? Because in non-coastal areas after tropical depressions, hurricanes, or other very heavy rainfall periods these species can cause more complaints (in a short period) than all of the other complaints you might receive during a whole year.