376 J. Aer. Mosq. CoNrnol Assoc. Vol. l, No. 3

cently ejected the virus while feeding on a car- lated from culicine mosquitoes in the Union of bohydrate source and the virus has yet to be South Africa. S. Afr. Med. J. 30:631-636. replenished into the salivary duct, and (3) W.H.O. 1972. Vector Ecology. Tech. Rep. Ser. "salivary there might be a gland escape bar- 50 I : l-38. rier" which prevents virus leaving these glands. This would be the situation when the produc- tion of infectious virus has been modulated to low levels. Such an escape barrier could explain TOXORHYNCHITES MOCTEZUMA, A the lowered transmission rates which have beerr POTENTIAL BIOLOGICAL CONTROL obtained after prolonged incubation periods AGENT IN TRINIDAD AND (Mclntosh and 1970, Mangiafico l97l). Jupp TOBAGO, W. I.1 I wish to thank the Director-General of National Health and Welfare, Pretoria. for DAVED. CHADEE' permission to publish. Ministry of Health and Environment, Vector Control Division, f3 Queen Street, St. Joseph, Trinidad, West Indies

ReferencesCited Toxorhynchitesmoctezuma (Dyar and Knab) fas Aitken, T. H. G. 1977. An in vitro feeding technique theobaldi (Dyar and Knab) in Knight and Stone for artificially demonstrating virus transmission by (1977)l has a wide distribution from Mexico in mosquitoes. Mosq. News 37:l3G- 133. Central America to Venezuela in South Chamberlain, R. W. 1968. Arboviruses, the America (Rubio et al. 1980; S. J. Heinemann, -borne viruses. Current Topics personal communication). In the Caribbean Microbiol. Immunol. 42:3U58. Basin, it has a limited distribution and is found Clarke, D. H. and Casals. 1958. Techniques J. for only in Trinidad and Tobago (Heinemann et al. haemagglutination and haemagglutination- 1980). It should be noted that Tx. theobaldi is inhibition with arthropod-borne viruses. Amer. J. now considered Trop. Med. Hyg. 7:561-573. a synonym of Tx. moctezuma (S. Heinemann, personal Hardy, J. L., E. J. Houk, L. D. Kramer and W. C. J. communication). Reeves, 1983. Intrinsic factors affecting vector In Trinidad and Tobago, threeToxorhynchites competence of mosquitoes for arboviruses. Annu. species have been recorded. Toxorbnchites moc- Rev. Entomol. 28:229-62. tezumn, Tx. iris (Dyar) [as mariae (Bowrroul) in J,rpp, P. G. and B. M. Mclntosh. 1970. Quantitative Knight and Stone (1977)l andTx. superhn (Dyar experiments on the vector capability of Culex '\Niedemann and Knab), of which Tx. iris andTx. superbus are (Culex) pipiens fatigans with West Nile found primarily in terresrrial and epiphytic and Sindbis viruses. Med. Entomol. 7:353-356. J. bromefiads (Heinemann et al. 1980). Toxorhyn- Kramer, L. D., L. Hardy, S. B. Presser and E. J. J. chites moctezuma, Houk. 1981. Dissemination barriers for Western on the other hand, has been equine encephalomyelitis virus in Culex tarsalis in- collected from bromeliads, treeholes. in tires and cans (Heinemann fected after ingestion of low viral doses. Am. J. et al. 1980, Chadee et al. Trop. Med. Hyg. 30:190-197. 1984). Mangiafico, J. A. 1971. Chikungunya virus infecrion In 1976, rhe Insect Vecror Control Division and transmission in five speciesof . Am. J. (IVCD) of the Ministry of Health and Envi- Trop. Med. Hyg. 20:642-45. ronment embarked on an Aedcs aegpti (Lin. Mclntosh, B. M. and P. G. Jupp. 1970. Attempts to naeus) Eradication program in Trinidad, W.I. transmit chikungunya virus with 6 species of mos- Tobago, however, is relatively free of Ae. aegypti quito. J. Med. Entomol. 7:615-618. but routine vigilance Mclean, D. M., A. M. Clarke, et al. 1974. Vector surveys are still conducted capability of Aed.esaegyph for California encephalitis twice yearly (Chadee et al. 1984). During sur- veys, larvae and dengue viruses at various temperatures. Can. J. and pupae of Tx. moctezumawere Microbiol. 20:255-262. collected in artificial containers in both Miles, J. A. R., J. S. Pillai and T. Maguire. 1973. Trinidad and Tobago. All immature stages Multiplication of Whataroa virus in mosquitoes. J. were collected and transported to the IVCD Med. Entomol. l0: 176- 185. laboratory, St. Joseph, Trinidad, where they Reeves, W. C. 1967. Factors that influence the proba- were subsequently identified by the author. bility of epidemics of Western equine, St. Louis and Table I summarizes the total collection of Tx. California encephalitis in California. Vector Views l4: I 3- 18. moctezunutfrom artificial containers in Trinidad Thomas, L. A. 1963. Distribution of the virus of t Western equine encephalomyelitis in the mosquito Published with approval from the Ministry of vector Culetctarsalis. Am. J. Hyg. 78:150-165. Health and Environment, Trinidad and Tobago, W.I. Weinbren, M. P., R. H. Kokenot and K. C. 2 Present Address: Department of Biological Sci- Smithburn. 1956. Strains of Sindbis-like virus iso- ences,The University. Dundee. DDI 4HN. UK. Srprrvnrn, 1985 J. Ar"r. Mosq. CoNrnol Assoc. 377

Tabfe l. Summary of the collections of Toxorhynchitesmoctentma in artificial containers in Trinidad and Tobago 1983-84.

Stages found No. of Type of (instars) samples container Localities Other species

Larvae (3) J Tires Flanigan Town, Trinidad Nov. 9, 1983 Ae. aegypti Larvae (4) 5 Water drums Flanigan Town, Trinidad Feb. 13, 1983 Ae. aegypti Pupa I Larvae (4) 5 Water drums La Canoa, Trinidad Feb. 17, 1984 Ae. aegyph Larvae (2) I Bucket La Canoa, Trinidad Feb. 12, 1984 Ae aeglpti Larvae (4) 2 Water drum Belle Garden, Tobago Jan. 20, 1983 Lm. d.urhamii and Cx. quinquefasciahu Larvae (4) 4 Water drum Delaford, Tobago May 20, 1983 Cx. quinquefasciatus Larvae (3) 4 Cans Pembroke, Tobago Jul. 3, 1984 Larvae (2) 2 Cans Calder Hall, Tobago Jul. 19, 1984 Larvae (3) 3 Tires Bacolet, Tobago Aug. 14, 1984 Larvae (4) 9 Basins Golden Grove, Tobago Aug. 15, 1984 i. uerttnt Larvae (3) 4 Water drurns Bethel, Tobago Aug. 16, 1984 Cx. qui.nqu efas ci. atus Larvae (2) 6 Water drums Goodwood, Tobago Aug. 26, 1984 Larvae (2) 3 Cans Patience Hall, Tobago Aug.26, 1984 Lm. durhamii Larvae (2) 3 Water drums Goodwood, Tobago Oct. I, 1984 TOTAL 50

and Tobago. The results indicate that the most stroy both feral and domestic populations of.Ae. frequently used artificial containers by aeglpti, which are found at various heights. ovipositing females were water drums (607o), Coincidentally, it should be noted thatTx. moc- followed by cans (l8Vo), tires (16%), basins (4%) tezuma are found in containers located within and buckets (2Vo). From a total of 50 positive shaded areas, similar to the localities where Ae. containers, 4OVo !r.ad Tx. moctezumnimmatures aegypti are found (Evans and Bevier (1969). alone. However, the type of containers with Thecollection of Tx. moctezuma from containers pure cultures of Tx. nxoctezurut were water known to harbor Ae aegypti (Chadee 1984) and drums, tires and cans, suggesting that all alter- other mosquito species indicates that a certain nate prey had been eaten. From the data col- degree of natural biological control is occurring lected, the frequency with which prey and in rural communities in Trinidad and Tobago. predator specieswere found together was 60%. As a result, Tx. moctezumaseems to be a suitable "candidate" In addition, four associated mosquito species species for biocontrol trials by were collected, namely, Ae. aegypti in Trinidad augmentative release in rural and urban situa- and, Culex quinquefasciatzs Say, Limatus d,urhami,i tions. Theobald and Ae. berlini Schick in Tobago. Specimens of Tx. moctezumahave been depos- Larvae of Toxorhynchites are especially pre- ited in the Insect Reference Collection at the daceous on the immature stages of other mos- Caribbean Epidemiology Centre (CAREC). The quitoes (Steffan 1975). In the United Statesand author wishes to thank Messrs S. B. Ferreira, G. in St. Maartin, W. I., laboratory and field trials Graham. I. Barrow. N. Mohommed and R. C. have been conducted on the use of Toxorhyn- Persad for field and laboratory assistance. Spe- ciiles mosquitoes to control Ae. aeglpti popula- cial thanks are due to Dr. R. Paul, Specialist tions (Gerberg and Visser 1978, Focks et al. Medical Officer (IVCD) and Dr. M. Nicols, 1982, 1983; Schuler and Beier 1983). County Medical Officer of Health (Tobago) for The collection of Tx. noctezuma in both natu- their assistance.In addition. I thank Dr. E. S. ral and artificial containers in Trinidad and Tikasingh, CAREC and Prof. P. S. Corbet, De- Tobago suggests that Tx. moctezuma utilizes a partment of Biological Science, The University, wide range of containers varying not only in Dundee, UK for their helpful advice and review size and water holding capacity but also in the of the manuscript. diameter of the exposed water surface. Moreover, the collections of Tx. moctezumafrom tree holes, terresterial and epiphytic bromeliads ReferencesCi,led (which vary in their vertical distribution) illus- Chadee,D. D. 1984.An evaluationof Temephosin trate the range of heights at which females of water drums in Trinidad, W. I. Mosq. News. this species will oviposit. As a result of its 44:51-53. oviposition habits, this species may serve to de- Chadee,D. D., N. K. Connell,A. Le Maitreand S. B. 378 J. Ar*. Mosq. CoNrnol Assoc. Vor". l, No. 3

Ferreira. I 984. Surveillance for Aedtsaegypti in To_ rn various magazines and they work quite well. bago, W.L Mosq. News 44:49O-493. The main objection to these was the price of Evans,B. R. and G. A. Bevier. 1969.Measurement of $2.08 each. For around $0. 18 per trap the same field populations of Aedesaegypti with the ovitrap in conversion can 1968. Mosq. News 29:347-353. be made. From an electronic Focks,D. A., S. R. Sackettand D. L. Bailev. 19g2. hobby or supply store, Field experiments on the control of Aedrs aegypti buy some axial lead diodes rared at 1000 PIV and, Culex quinquefasciatusby Toxorhynchitr, ,uiltu (peak inverse voltage) at I amp. They come in rutilus (Diptera: Culicidae).J. Med Entomol. packages of various quantities and prices, usu- l9:336-339. ally priced at 90.18 to 90.30 each. There is a Focks,D. A., S. R. Sackett,D. A. Dame and D. L. band at one end of the diode to determine Bailey. 1983. Toxorbnchitesrutilus (Diptera: rutihn polarity. In this application it makes no dif- Culicidae).Field studieson dispersaland oviposi_ ference which way the diode is installed. tion in the contextof the bio-controlof urban con- First, disconnect one of the wires attached to tainer breeding mosquitoes.J. Med. Entomol. 20:383-390. the bulb socker and atrach one lead of the diode Gerberg, E. L. and W. W. Visser. 1928.preliminarv to this point. Then, solder the other lead of the field trials for biological conrrol of Aedcsaegypti by diode to the wire that was just removed. It is means of Tx. brnipalpus-a predatory mosouito advisable to use some type of heat sink while .Mosq. News. 38:lg7-20b. soldering to prevent damage to the diode. Alli- Heinemann, S. G., T. H. G. Aitken and J. N. Belkin. gator clips or hemostats work fine. Finallv. 1980.Collection records of the projectl.Mosquitoes tape the exposed lead to prevent any possibie of Middle America" 14.Trinidad and tobago 1TR, shorts to the light trap body. The diode TRM,'IOB), Mosq.Syst. l2:l29-284. must be installed in this manner (Fig. l) and cannot be Knight, K. L. and A. Stone. 1977.A catalogof the placed in the main line mosquitoes of the world (Diptera: Culicidae) cord because the farr motor requires ThomasSay Foundation, Entomol. Soc. Am. Vol.6. AC to run. 6ll p. With this conversion the bulbs burn dimmer Rubio, Y. D., C. E. Rodriguez,J.A. Machado-Allison than normal. If 15 or 25 watt bulbs were useci and J. A. leon. 1980.Algunos aspectosdel com_ before, it is necessary to use 60 watt bulbs to portamiento de ToxorhynchitasTheobald (Diptera: achieve approximately the same illumination. Culicidae). Acta Cient.Venezolana. 3l:34f-851. To determine what was happening, the follow- Schuler,T. C. and J. C. Beier. 1983. Oviposition ing measurements were made. dynamics of two released speciesof Toxorhynchites With a 15 watt bulb connected directly to 120 (Diptera: Culicidae)and potential prey species.J. volts Med. Entomol. 20:371-376. AC without the diode installed, it would be expected (I:P/E: Steffan, W. A. 1975.Systematics and biologicalcon_ from Ohm's law l51120) that trol potential of Toxorhynchita_s(Diptera: Culicidae). the bulb would draw 0.125 amps. When actually Mosq. Syst.7:5V67. measured, however, the bulb drew 0. 108 amps and, by the same formula, this yields 12.9 watts. This is within 20% which is an acceptable toler- ance. With the diode installed, the voltage mea- sured across the bulb was 54 volts DC part of NEW JERSEYLICHT which was caused by the forward resistance of' TRAP MODIFICATION TO the diode. The measured current in this circuit EXTEND BULB LIFE was 0.056 amps and, again using the above formula, this yields 3 watts. Since the bulb. H. W. WESTervo D. L. CASHMAN which was rated at 15 wats rvas only drawing 3 PrincessAnne Mosquito Control Commission,1848 watts and operating on half of the AC cycle, the PleasantRidge Rd., Virginia Beach,VA 23457 brightness was greatly diminished. Hence the reason for using a 60 watt bulb to achieve ap- For the past several seasons while using the New Jersey light trap for monitoring of adult mosquito populations, it was noticed that the light bulbs used had a high failure rate. During the 1983 season our commission replaced 32 bulbs in the 12 traps used. We felt that the best solution to the problem AC ln was to convert the traps to operate the bulbs on DC voltage instead of AC. One method of achieving this is to install the little discs that are inserted into the bulb socket and replacing the Fig. L Schematic diagram showing bulb over the disc. These have been advertised placemenr of diode.