Journal of the American Mosquito Control Association, 13(4):356-36O, 1997 Copyright A 1997 by the American Mosquito Control Association, Inc. STUDY ON THE FLYING HEIGHT OF AEDES CASPIUS AND CULEX PIPIENS FEMALES IN THE PO DELTA AREA, ITALYI ROMEO BELLINI, RODOLFO VERONESI, STEFANO DRAGHETTI er.ro MARCO CARRIERI Centro Agicoltura e Ambiente, Via di Mezzo Levante 2233, 40014 Crevalcore, Italy "Ancona ABSTRACT. We have studied the vertical distribution of Culicidae in the di Bellocchio" protected (Regional area Park of the Po Delta, Emilia-Romagna, Italy) by means of nonilluminated CDC traps baited with COr. Traps were placed at heights of 1.5, 3, 4, and 5 m from the ground in open areas and at t5, 3, 4,5,6, and 7 m in wooded areas. We calculated the average flying height of the species caught, i.e., in order of decreasing flying height, Culex pipiens Linnaeus s.1., Culex modestis Ficalbi, Ciquiltettidli richiardii (Ficalbi), Aedes detritus (Haliday), Aedes caspius (Pallas). We also calculated the linear regiession lines for both sites and found that 9OVo of Ae. caspius flew within a height of 1.64 m from the ground level, 95Va within 2.68 m, and gOVo 99Vo at a height not exceeding 4 m; whereas of Cx. pipiens moved within 3.45 m from the ground level, 95Vo within 4.O2 m, and 99Vo within 4.76 m. The vertical distributions of Ae. caspius and Cx. pipi"nt did not vary significantly over the seasons and were not affected by the presence of treeJor variations in temperature and wind velocity within the range of measurements obtained. Thi data obtained provide useful informition for planning Ae. caspius control measures based on a mechanical barrier capable oi preventing mosquitoes from moving toward residential settlements and tourist resorts bordering on the protected area ai an aiternative to aerial treatment with the larvicide Bacillus thuringiensis subsp. lsraelensrs. INTRODUCTION lensis De Barjac. However, this approach to con- trolling Ae. caspius does not guarantee optimum The heights at which Culicidae fly have been control efficacy, and at certain times during the sea- studied in various environments and analyses made son, the airplanes used for spraying cause major of the behavior of several species (Snow and pick- disturbances among the birds that nest in the pro- ard 1956, Love et al. 1963, Davies et al. 1971, Ser- tected wetlands. Therefore, alternative control strat- vice 197I, Pfuntner et al. 1988, Mian et al. 1990). egies need to be found, so as to improve the effec- Extensive studies have been carried out on the ver- tiveness of the anti-Culicidae campaign. Among tical distribution of sylvan yellow fever vectors in these, the erection of a physical barrier to prevent Africa (Haddow et al. l94T,Mattingly 1949, Goma females in a protected area from moving to an ad- 1965, Snow 1975, Gillies and Wilkes 1976). jacent tourist resort may be viable. Understanding However, no research appears to have been con- the composition of the local mosquito fauna and the ducted on the vertical distribution of Aedes caspius vertical distribution of the adult mosquitoes is es- (Pallas). A Palearctic species that is particularly sential in order to assess the necessary parameters well adapted to coastal environments, Ae. caspius for erecting such a barrier. tolerates varying levels of salinity in larval breed- ing sites, and larval development is linked to the alternating dry and flood regimes of areas where MATERIALS AND METHODS eggs are laid. Its marked anthropophily, dispersal, Ttvo flxed stations, approximately 150 m apart, and population size cause infestations to be very were selected for conducting this study, in order to annoying in the coastal tourist resorts around the adequately represent the landscape and vegetation Po Delta (Emilia-Romagna, Italy), so much so that of the area. Both sites bordered on the natural pro- they significantly damage the tourist economy of tected area: one was located in a wood consisting the area (Bellini and Veronesi 1994, Veronesi et al. mainly of l0-l3-m-high Pinus pinea L.; the other 1995). It is one of the most important pests in the was located in an open area, with vegetation con- area and the focus of most mosquito control cam- sisting of grass and shrubs up to 1.5 m in height. paigns. Six traps were positioned in the wooded area at The main aim of this work was to study the fly- 1.5, 3, 4,5, 6, and 7 m from the ground, and 4 ing height of mosquito species developing in the "Ancona were placed in the open :uea at I.5,3,4, and 5 m di Bellocchio" protected area, where a from the ground. We decided to sample up to a large Ae. caspius breeding site exists, and control higher level in the wooded area in order to check campaigns have so far been conducted by aerial for the presence of females hunting for blood meals application of Bacillus thuringiensis subsp. israe- in the higher foliage (Burgess and Haufe 1960). In the open area, the traps were stacked at varying "Culicids heights pole. I Study conducted within the project, Control on the same In the wooded area, the Programme in the Coastal Tourist Resorts Within the Po traps were positioned on different trees within a Delta Area," financed by Emilia-Romagna Tourist Re- radius of 15 m, with the 5-m and 7-m-high traps gional Bureau (Regional Law n.15/91) together with the on the same tree. The traps used were nonillumi- municipalities of Comacchio and Ravenna. nated COr-baited CDC traps, each containing 500 356 DpcpMssn 1997 Flynqc Hprosr op Aeoxs cAsprus 357 "Ancona Table 1. Culicidae species caught by CO, traps (females/trap/night) in the 2 stations located in the di Bellocchio" area, Emilia-Romagna, Italy, 1996. Wooded area Open area Total Species (6 traps x 13 nights) (4 traps x 13 nights) specimens caught Aedes caspius 8.r (3O.13Vo) 67.0 (72.50Vo) 4,117 (59.65Vo) Aedes detritus 0.01 (0.057o) O.3(O.29Vo) 15 (O.22so) Culex pipiens 17.6 (65.76Vo) 21.4(23.ll%o) 2,488 (36.O5Vo) Culex modestus 1.1(3.96Eo) 3.6 (3.9l%o) 27r (3.93Vo) Culiseta annulata 0 O.O4(O.O4Vo) 2 (O.O3Vo) C oquille ttidia richiardii O.O2(O.lO7o\ O.13(O.l57o) 9 (O.l3Vo) Total 26.8 (lOOVo) 92.5 (lOOVo) 6,902 (lOOEo) g solid CO, and provided with 2 holes in the bottom was less than L m,/secwith catcheswhen wind ve- to ensure the emission of 200-300 mVmin during locity exceeded I m/sec. Besides affecting flying the catching period. These traps are widely used for ability (Bidlingmayer et al. 1995), the wind may monitoring Culicidae populations and are regarded cause CO2, which tends to spread downward be- as among the most reliable (Meyer et al. 1984, Re- causeit is heavier than air, to dispersehorizontally. isen and Pfuntner 1987). Similarly, we analyzed any influence of tempera- The experiment was conducted from May 22 to ture on flying height by comparing the flying October 3, 1996, following some preliminary tests heights at temperatures above and below 18'C in 1995 to define procedures and select the most (Bidlingmayer et al. 1995). appropriate stations. Tfaps were placed in both sta- The relation between the number of catches in tions one night a week, from at least I h before the 2 stations was studied by analyzing data by sunsetuntil the following morning. In case of rain means of a z-way ANOVA, after the angular con- or strong wind, the catch was repeatedduring the version of percentageresults, followed by Duncan's same week. Metereological data on average tem- test. To ensure homogeneity of criteria in compar- perature, rainfall, wind velocity, and wind direction ing the open and wooded areas,only traps placed for the nights during which the experiments were at the same height and specimens caught on the conducted were obtained from the Volano station, same dates were considered. Subsequently, average about 20 km away. flying height was calculated using Tukey's test to Any influence from weather conditions on flight process data obtained from both stations, having behavior was assessedfor Ae. caspius and Culex been previously analyzedwith a one-way ANOVA. pipiens Linnaeus s./., the 2 speciesfor which a suf- The linear regressionswere obtained by the loga- ficient number of specimenswere caught. To this rithmic conversion ofheights (9) and percentageof purpose, we investigated the weather conditions re- catches (cr) using model ln(l + cr) : a + b ln(p). corded in the course of the typical period of daily Covariance analysis (ANCOVA) was used to com- activity for both species (unpublished data), from pare regressionlines. 1900 to 22W h and from 0500 to 0800 h the fol- lowing day for Ae. caspius, and from 2000 to 0600 h of the following day for Cx. pipiens. Becauseof RESULTS the distance of the weather station from the sam- The pling site, we assumed that variations in tempera- Culicidae speciescaught were Ae. caspius, Aedes (Haliday), pipiens, ture and wind velocity between the 2 sites would detritus Cx. Culex mo- (Ficalbi), not be significant. The influence of the wind was destus Ficalb| Coquillettidia rtchiardil (Schrank). assessedby comparing catcheswhen wind velocity and Culiseta annulata The most numerous species found in both sta- tions were Ae. caspius and Cr. pipiens (Table 1), Table 2. Catches of Aedes caspius and Cul.ex pipiens which are known to be a major nuisance in the area obtained at various sampling heights, Bellocchio, around the Po Delta (Bellini and Veronesi 1994, Emilia-Romagna, Italy, 1996.