Maximum radius of carbon dioxide baited trap impact in woodland: implications for host-finding by mosquitoes

CDC traps were used to determine the maximum radius of carbon dioxide attraction within forest habitat (a forest plant community with Carpino betuli-Quercetum roburis). A central CDC trap with dry ice (CO₂) was set as the source of attractant (Ck). Around Ck trap two circles (A and B) of CDC traps without attractants were placed. Circle A was constituted of 6 CDC traps and Circles B with 12 CDC traps. Radius from Circle A and B to the Ck trap were used to determine CO₂ maximum range. During the experiment, the average emissions of CO₂ were 0.08 to 0.1 g s^?1. Regarding the data, optimal radius attraction where CO₂ was affected on mosquitoes was between 55 and 70 m from the source. Results propose that the distance between traps should be greater than 140 m, to ensure the absence of bias by each of the traps. Changes in CO₂ maximum concentration and wind velocity directly affected the catch of different species. The number of Ochlerotatus sticticus collected was positively correlated with wind speed.     

The flight distances of floodwater mosquitoes (<Emphasis Type="Italic">Aedes vexans,Ochlerotatus sticticus</Emphasis> and <Emphasis Type="Italic">Ochlerotatus caspius</Emphasis>) in Osijek,Eastern Croatia

In spring 2004, the mark-release-recapture study was conducted in the Osijek area, covering the total of 171 km², to describe dispersal pattern of three floodwater mosquito species (Aedes vexans, Ochlerotatus sticticus and Oc. caspius). Forty CO₂ baited Center for Disease Control and Prevention (CDC) traps were set at distances varying from 0.95 to 16.7 km from release site. Fifty thousand mosquitoes were released, and a total of 22 marked mosquitoes were recaptured in 12 traps, 82% of which were collected in the first six days after release. The maximum distance of recaptured mosquito (Oc. sticticus) was found at 11.68 km from the release site. During the study, the average dispersal rate per day for mosquitoes ranged from 0.96 km to 3.6 km in regard to different species.     

Seasonal dynamics of the Anopheles maculipennis complex in Osijek, Croatia.

Malaria was once endemic in the Osijek region of Croatia and although it has been eradicated, there are still several vector species of the Anopheles maculipennis complex in this area. During an eight-year investigation, using CDC traps with CO2 as an attractant, we collected a total of 3,508 mosquitoes. We determined the dynamics of members of this complex and found that they varied considerably with an average of two generations per season. Cross-correlations indicated that the Spearman's Index between the abundance rate and the water level was the highest 12 and 24 d before traps were set. This suggests that the long-term high water level created better conditions for continuous breeding of mosquitoes, which contributed to a significant increase in abundance rates of all species in the complex.     

Updated checklist of the mosquitoes (Diptera: Culicidae) of Croatia

Improvement of morphological and molecular identification methods allows the detection of new species of mosquitoes. The mosquito fauna of Croatia currently includes 52 species, belonging to eight genera, including Anopheles (12 species), Aedes (24 species), Coquillettidia (one species), Culex (seven species), Culiseta (six species), Orthopodomyia (one species), and Uranotaenia (one species). This is an updated checklist, which includes five new species found in Croatian mosquito fauna. Two of these are invasive mosquito species, Aedes albopictus (Skuse, 1895) and Aedes japonicus (Theobald 1901), which are spreading across Europe and Croatia. The other three species, Culex laticinctus (Edwards 1913), Culex torrentium (Martini 1925), and Anopheles daciae (Linton, Nicolescu & Harbach 2004) are autochthonous species which haven't been recorded so far. Since there are several more invasive species spreading across Europe, we assume that this is not the final list.     

PSA‐NCAM expression in the teleost optic tectum is related to ecological niche and use of vision in finding food

In this study, tangential migration and neuronal connectivity organization were analysed in the optic tectum of seven different teleosts through the expression of polysialylated neural cell adhesion molecule (PSA‐NCAM) in response to ecological niche and use of vision. Reduced PSA‐NCAM expression in rainbow trout Oncorhynchus mykiss optic tectum occurred in efferent layers, while in pike Esox lucius and zebrafish Danio rerio it occurred in afferent and efferent layers. Zander Sander lucioperca and European eel Anguilla anguilla had very low PSA‐NCAM expression in all tectal layers except in the stratum marginale. Common carp Cyprinus carpio and wels catfish Silurus glanis had the same intensity of PSA‐NCAM expression in all tectal layers. The optic tectum of all studied fishes was also a site of tangential migration with sustained PSA‐NCAM and c‐series ganglioside expression. Anti‐c‐series ganglioside immunoreactivity was observed in all tectal layers of all analysed fishes, even in layers where PSA‐NCAM expression was reduced. Since the optic tectum is indispensable for visually guided prey capture, stabilization of synaptic contact and decrease of neurogenesis and tangential migration in the visual map are an expected adjustment to ecological niche. The authors hypothesize that this stabilization would probably be achieved by down‐regulation of PSA‐NCAM rather than c‐series of ganglioside.     

Influence of molting on efficacy of two functionally different larvicides: Bti and temephos

The sensitivity of the second, third (L3), and fourth (L4) instars of Culex pipiens L. and Ochlerotatus sticticus (Meigen) to two larvicides, temephos and Bacillus thuringiensis variety israelensis (Bti) was tested with and without molting occurring in the experiments. In the first experiment for both tested mosquito species, LC50 values increased from the second to the fourth instar when tested against temephos, whereas for Bti the opposite trend was observed. The highest LC50 value was found for fourth instars of Cx. pipens (0.00405 mg/liter) against temephos and for second instars of Oc. sticticus (0.267 mg/liter) against Bti. The determined LC50 values for the second and third instars of both species decreased with an increased number of molted larvae in the experiments with temephos. For the experiments with Bti molting did not have any significant influence on LC50 values, except a small increase in toxicity during the L3/L4 molt of Oc. sticticus. These findings could help assess and define larviciding, as well as influence the quantity of larvicides needed for an efficient treatment.     

Response of Tabanidae (Diptera) to different natural attractants.

The response of female tabanids to natural attractants was studied in the Monjoros Forest along the Nature Park Kopacki rit in eastern Croatia. Tabanids were caught in canopy traps baited with either aged cow, horse, sheep, or pig urine and also in unbaited traps. Tabanids were collected in a significantly higher numbers in traps baited with natural attractants compared to unbaited traps. The number of females of Tabanus bromius, Tabanus maculicornis, Tabanus tergestinus, and Hybomitra bimaculata collected from canopy traps baited with cow urine and traps baited with other natural attractants differed significantly. Females of Haematopota pluvialis were also collected more frequently in canopy traps baited with aged cow urine than in those with aged horse urine, but this difference was not significant. However, the number of females of Haematopota pluvialis collected from canopy traps baited with other natural attractants (sheep and pig urine) differed significantly when compared with aged cow urine baited traps. Canopy traps baited with aged cow urine collected significantly more Tabanus sudeticus than did traps baited with aged pig urine. Finally, the aged cow urine baited canopy traps collected 51 times more tabanids than unbaited traps, while aged horse, aged sheep, and aged pig urine baited traps collected 36, 30, and 22 times as many tabanids, respectively, than unbaited traps.     

Flood pulses drive the temporal dynamics of assemblages of aquatic insects (Heteroptera and Coleoptera) in a temperate floodplain

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Seasonal dynamics of mosquitoes (Diptera: Culicidae) in Osijek (Croatia) for the period 1995–2004

The ten year research (1995–2004) of adult mosquitoes in the area of Osijek by dry ice baited CDC traps has provided significant information on mosquito species, species prevalence, their dynamics and seasonal activity. A total of 207,136 adult mosquitoes comprising twenty species belonging to the following genera: Anopheles, Ochlerotatus, Aedes, Culex, Coquillettidia, Culiseta and Uranotaenia were collected. The seven most common species collected during this study were: Aedes vexans (75.6%), Ochlerotatus sticticus (13.3%), Culex pipiens complex (5.9%), Anopheles maculipennis complex (1.9%), Oc. cantans (0.9%), Oc. caspius (0.6%) and Oc. excrucians (0.6%). The temporal changes in the relative abundance of the twenty mosquito species in the Osijek area were reflected in three peaks: in May, July and September. Seasonal population dynamics differed between years and between mosquito species in relation to wetland, urban and forest habitats and was influenced by water level of the Drava and the Danube rivers.     

Efficacy of mosquito attractants in various habitats of a floodplain

Efficacy of different mosquito attractants was invesigated at four sites in three plant communities (Galio-Salicetum albae, Populetum nigro-albae, Genisto elatae-Quercetum roboris) of flooded and forest habitats in Kopački rit Nature Park, Croatia. The attractants were: dry ice, horse urine, horse urine + acetone, acetone, 1-octen-3-ol and ammonium hydroxide baited CDC traps. A total of 11,441 mosquito specimens of 12 species were collected. Aedes vexans (91.43%) was the most numerous species. A statistically significant difference between the efficacy of dry ice and the other attractants was shown, whereas there was no difference between the other attractants. A greater number of specimens and species number were noted in the flooded plant communities (Populetum nigro-albae). The response of Ae. vexans to dry ice was higher in flooded sites, and it was significantly lower in forest habitat (Genisto elatae-Quercetum roboris) according to fuzzy c-means cluster analysis. The same analysis shows a higher efficacy of other attractants (horse urine, horse urine + acetone, acetone, octenol and ammonium hydroxide) in forest habitat when compared to the flooded area habitats.