VIRGINIA MOSQUITO CONTROL ASSOCIATION

Kirby R. Foley, Sr.

900 Hollowell Lane

Chesapeake, Va. 23320

kfoley@mail.city.chesapeake.va.us

Phone: (757) 673-3932

Fax:       (757) 966-5236

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            [REFERENCES CITED]

Collection of Culex tarsalis (Coquillett) in Southeastern Virginia

Jason W. Williams, Penelope A. Cuffee, and Kirby R. Foley, Sr.

Abstract. In 2003, Culex tarsalis was collected in southeastern Virginia. There is only

 one previous record for this species in Virginia. Also included are: a habitat description

 for the site of collection, diagnostic characters for the species, and a short discussion.

KEY WORDS.  Culex tarsalis, Virginia, rare species

            This article describes the collection of Culex tarsalis (Coquillett) in Southeastern

 Virginia. The single female was collected in a carbon dioxide baited modified-CDC trap

 during the night of November 5-6, 2003. The trap was located at 1944 South Military

 Highway in Chesapeake, Virginia, in a low, marshy wooded strip near a larger wooded

 area, and also near a large marshy field with head high vegetation. A fence company and

 a trailer court are very near the site and across the highway is a large shopping center.

 The authors’ initial identification was confirmed by Dr. Bruce Harrison. Dyar (1928)

 published the only other record of this species in Virginia, based on a single specimen

 collected in Quantico, Virginia, on October 18, 1926 (B.A. Harrison, personal

 communication). The Dyar (1928) record was overlooked by Darsie and Ward (1981)

 and Harrison et al. (2002).  

             Although Culex tarsalis is brown and approximately the same size as most of the

 species in the subgenus Culex, it has a number of unique characters that make it very easy

 to identify and to distinguish from other species such as Cx. restuans. The Cx. restuans

 does have a partial band of pale scales on the ventral side of the proboscis, and may have

 pale bands on the hind tarsi. The Cx. tarsalis that was trapped, has a complete band

 around the proboscis, has wide overlapping bands on the joints of hind tarsi, and some

 banding on the middle and front legs. Also, the ventral side of the abdomen is pale-scaled

 with V-shaped marking of dark scales on each sternite, the base of the V at the median

 anterior margin. Some good references to look up the taxonomic descriptions are:  

 Bohart and Washino 1978, Carpenter and LaCasse 1955, Darsie and Ward 1981, Meyer

 and Durso Revised 1998, Slaff and Apperson 1989.

             This species has a very wide distribution in North America, extending from

 Canada to Mexico (Carpenter and LaCasse 1955). In the United States it is primarily a

 mid-western and western species. East of the Mississippi River it is less common and rare

 or absent in some states along the east coast. Darsie and Ward (1989) identified

 Delaware, Maryland, District of Columbia, North Carolina, Virginia (overlooking the

 record of Dyar 1928), and West Virginia in the Mid-Atlantic Region as not having

 records for Cx. tarsalis. Lesser et al. (1977) reported the collection of a single female in

 New Jersey in 1975, and considered the specimen an accidental introduction by one of

 the many tourists visiting the area. However, Crans et al. (1979) collected 9 additional

 specimens in 1977, and at least one female was 75 km from the collection site in 1975.

 These last authors reported that Cx. tarsalis had established a small breeding population

 in New Jersey. Occasional specimens of Cx. tarsalis are still collected to the present in

 this area of New Jersey (W.J. Crans, personal communication).

             Culex tarsalis is the primary vector of Western Equine encephalitis and St. Louis

 encephalitis  in many parts of the western states, and has also been found infected with

 several other viruses that can cause human illness (Bohart and Washino 1978).

             In conclusion, the collections of Cx. tarsalis in Chesapeake (2003) and in

 Quantico (1926) are rare fines. Only the future will determine if the species will remain

 an occasional rare collection in Virginia.

             The authors acknowledge the Commissioners of the Chesapeake Mosquito

 Control Commission and Gene Payne, Director, Chesapeake Mosquito Control District,

 for their continuing support of mosquito surveillance and arbovirus studies. We also

 thank Dr. Bruce A. Harrison, North Carolina Department of Environment and Natural

 Resources, for confirming the specimen, his encouragement to publish this information,

 and for reviewing the manuscript.

 -

REFERENCES CITED

 Bohart RM, Washino RK. 1978. Mosquitoes of California. Third Edition. Univ Calif Div

 Agric Sci, Number 4084, Berkeley, CA.

 Carpenter SJ, LaCasse WJ. 1955. Mosquitoes of North America (north of Mexico). Univ

 Calif Press, Berkeley, CA.

 Crans WJ, Lesser F, Candeletti T. 1979. Recent distribution records of Culex tarsalis in

 New Jersey. Mosq News 39:244-247.

 Darsie, RF, Jr., Ward RA.  1981  Identification and geographical distribution of the

 mosquitoes of North America, north of Mexico.  Mosq Syst Suppl 1:1-313.

 Dyar HG. 1928.  The mosquitoes of the Americas.  Carnegie Institute Washington,

 Publication 387, Washington, DC.

 Harrison BA, Whitt PB, Cope SE, Payne GR, Rankin SE, Bohn LJ, Stell FM, Neely CJ.

 002.   Mosquitoes (Diptera:  Culicidae) collected near the Great Dismal Swamp:  new

 state records, notes on certain species, and a revised checklist for Virginia.  Proc Entomol

 Soc Wash 104:655-662.

 King WV, Bradley GH, Smith CN, McDuffie WC.  1960.   A handbook of the mosquitoes

             Of the southeastern United States.  U S Dept Agric Handbook 173:1-188.

 Lesser F, Candeletti T, Crans W.  1977.  Culex tarsalis in New Jersey.  Mosq News

             37:290.

 Meyer RP, Durso SL. 1998. Identification of the Mosquitoes of California. Publ  of

 Mosquito and Vector Control Association of California

 Nelson MJ.  1971.  Mosquito studies XXVI.  Winter biology of Culex tarsalis in Imperial

 Valley, California.  Contrib Am Entomol Inst (Ann Arbor) 7(6):1-56.

 Slaff M, Apperson CS.  1989.  A key to the mosquitoes of North Carolina and the Mid-

 Atlantic states.  N C State Univ, Agric EXT Serv Publ AG-412:1-38

 Snow WE, Pickard E.  1956.  Seasonal history of Culex tarsalis and associated species in

 larval habitats of the Tennessee Valley Region.  Mosq News 16:143-148.

The Collection of Psorophora horrida (Dyar and Knab) in Southeastern Virginia

Norman A. Grefe

Introduction

Psorophora ferox and Psorophora horrida are two morphologically similar species that occur in Virginia, with the former  being the more common of the two. The distribution of Ps. horrida in Virginia is not well understood. The only published record of its collection in the state was mention in Dorer, et. al. (1944) based on a collection made by F.C. Pratt from Shenandoah County in 1904 (Harrison, personal communication). Ps. horrida may be more common in Virginia than believed, but given the morphological similarity of the two species, is often identified as Ps. ferox. This article describes the collection of Psorophora horrida in eastern Virginia during the summer of 2003. Habitat, distribution, and the diagnostic characters used to differentiate Ps. horrida from ferox are also discussed.

Method of Collection and Species Confirmation

Approximately 76 adult female Psorophora horrida specimens were collected via mechanical aspirator during the late morning hours (1030-1130) of July 5, 2003 in Isle of Wight County, Virginia. Ps. horrida were collected along with Ps. ferox, Ochlerotatus infirmatus, and Ochlerotatus sticticus, all of which were aspirated after landing on the author. The habitat from which these specimens were collected was a mixed deciduous and pine forest, with permanent cypress swamps and temporary woodland pools nearby. Specimens were identified at the City of Suffolk's mosquito lab, with the differention of Ps. horrida from Ps. ferox based on Slaff and Apperson (1989). A number of Ps. horrida specimens were mailed the following week to Dr. Bruce Harrison of the North Carolina Department of Environment and Natural Resources for confirmation.

Species Description

Psorophora horrida are morphologically very similar to Ps. ferox, particularly with regards to the white tarsomeres 4 and 5 on the hind legs. This may lead to misidentification of species if this character is the only one used for species determination. While the integument of the scutum for both species is dark, scutal scale patterns are diagnostic for the respective species. The scutum of Ps. ferox is speckled with small yellow/gold scales that occur in no particular pattern. However, with Ps. horrida, the light (white/cream) colored scales occur in patches on the scutal fossa and extend posteriorlly towards the supraalar area. Also diagnostic of Ps. horrida are the dark brown/bronze scutal midline scales that create a longitudinal dark line down the length of the scutum that is discernable without the aid of magnification. Another prominent character used for differentiating Ps. horrida from ferox is the median white scale patch on abdominal tergum I of Ps. horrida and purple on Ps. ferox.

In addition to the above diagnostic characters, Harrison and Whitt (1996) found six additional characters that can be used to differentiate the two species. Number of scales on the median half of the pedicel, the presence or absence of a subspiracular scale patch, and the color of the scutal scales just above the paratergite and prealar knob are all reliable diagnostic characters and are important for accurate identification in situations where the specimens may be lacking scales or are in otherwise less than pristine condition. The presence or absence of white subspiracular scales is easily seen on the dark thoracic pleura of specimens of these two species. This work should be consulted for a more detailed treatment of the morphological differences between Psorophora horrida and ferox.

Biology and Distribution of Psorophora horrida

Psorophora horrida and ferox are both summer, temporary woodland pool mosquitoes, thus they tend to occur together along with other mosquito species common to this habitat. Ps. horrida eggs hatch shortly after flooding and their larvae  develop rapidly (Carpenter and LaCasse, 1955). Female Ps. horrida are very aggressive and seem to attack the upper extremities more so than the lower and frequently observed probing for a blood meal through clothing.

Psorophora horrida occur from the southeastern United States, west to Texas and Nebraska, and north to Ohio and Pennsylvannia (Carpenter and LaCasse, 1955). Compared to Virginia, the range of this species in North Carolina is better understood and has been collected  from a number of piedmont counties (Harrison and Whitt, 1996). As of this writing, Psorophora horrida have been confirmed from only two Virginia Counties: Shenandoah County (1904) and Isle of Wight County (2003).

Conclusion

The confirmed collection of Psorophora horrida in southeastern Virginia during the summer of 2003 raises questions as to the distribution of this species in the state. While the collection of this species in Isle of Wight County may have simply been an isolated occurrence, Ps. horrida may be more common in Virginia than believed, but often misidentified due to morphological similarities to Ps. ferox (e.g.,white hind tarsomeres).

Acknowledgment

The author would like to thank Dr. Bruce Harrison from the North Carolina Department of Environment and Natural Resources for his guidance in putting together this brief note.

            References  

         Carpenter, S.J. and LaCasse, W.J. 1955. Mosquitoes of North America. Berkeley: University of California Press.

    Harbach, R.E. and Knight, K.L. 1980. Taxonomists' glossary of mosquito anatomy. Marlton, NJ: Plexus Publishing, Inc.

            Harrison, B.A., Whitt, P.B. 1996. Identifying Psorophora horrida females in North Carolina (Diptera: Culicidae). J.Am. Mosq. Control Assoc. 12: 727-727.

    Slaff, M. and Apperson, C. 1989. A Key to the Mosquitoes of North Carolina and the Mid-Atlatic States. North Carolina Agricultural Extension Service.

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