Pál Boda

Why do red and dark-coloured cars lure aquatic insects? The attraction of water insects to car paintwork explained by reflection-polarization signals

We reveal here the visual ecological reasons for the phenomenon that aquatic insects often land on red, black and dark-coloured cars. Monitoring the numbers of aquatic beetles and bugs attracted to shiny black, white, red and yellow horizontal plastic sheets, we found that red and black reflectors are equally highly attractive to water insects, while yellow and white reflectors are unattractive. The reflection–polarization patterns of black, white, red and yellow cars were measured in the red, green and blue parts of the spectrum. In the blue and green, the degree of linear polarization p of light reflected from red and black cars is high and the direction of polarization of light reflected from red and black car roofs, bonnets and boots is nearly horizontal. Thus, the horizontal surfaces of red and black cars are highly attractive to red-blind polarotactic water insects. The p of light reflected from the horizontal surfaces of yellow and white cars is low and its direction of polarization is usually not horizontal. Consequently, yellow and white cars are unattractive to polarotactic water insects. The visual deception of aquatic insects by cars can be explained solely by the reflection–polarizational characteristics of the car paintwork.

When do beetles and bugs fly? A unified scheme for describing seasonal flight behaviour of highly dispersing primary aquatic insects

Changes of seasonal dispersal flight were investigated based on a wide spectrum of aquatic Heteroptera and Coleoptera species. We hypothesized that species or groups of species can be characterized by various seasonal patterns of dispersal flight. Dispersal activity was studied in a lowland marsh located in NE Hungary during a 30-week long monitoring period. Insects were attracted to highly polarising horizontal shiny black plastic sheets laid onto the ground. There are no periods of the year (from April till October) when insects are not rising into the air, but species have various seasonal flight activity. Dispersal flight activity of 45 species could be described. These activities assessed based on a seasonal approach and proportional classification. Based on these results, three seasonal patterns and twelve sub-patterns were defined. Comparing the observed patterns with previously reported dispersal activity data, we argue that observations found in the literature fit well with patterns defined here, therefore, to assess the dispersal behaviour, a unified scheme can be established. Owing to this unified scheme, the seasonal dispersal activity of primary aquatic insects observed in different studies becomes highly comparable. This scheme can be a useful tool for assessing dispersal behaviour of insects across other geographic regions.

Phototaxis and polarotaxis hand in hand: night dispersal flight of aquatic insects distracted synergistically by light intensity and reflection polarization

Based on an earlier observation in the field, we hypothesized that light intensity and horizontally polarized reflected light may strongly influence the flight behaviour of night-active aquatic insects. We assumed that phototaxis and polarotaxis together have a more harmful effect on the dispersal flight of these insects than they would have separately. We tested this hypothesis in a multiple-choice field experiment using horizontal test surfaces laid on the ground. We offered simultaneously the following visual stimuli for aerial aquatic insects: (1) lamplit matte black canvas inducing phototaxis alone, (2) unlit shiny black plastic sheet eliciting polarotaxis alone, (3) lamplit shiny black plastic sheet inducing simultaneously phototaxis and polarotaxis, and (4) unlit matte black canvas as a visually unattractive control. The unlit matte black canvas trapped only a negligible number (13) of water insects. The sum (16,432) of the total numbers of water beetles and bugs captured on the lamplit matte black canvas (7,922) and the unlit shiny black plastic sheet (8,510) was much smaller than the total catch (29,682) caught on the lamplit shiny black plastic sheet. This provides experimental evidence for the synergistic interaction of phototaxis (elicited by the unpolarized direct lamplight) and polarotaxis (induced by the strongly and horizontally polarized plastic-reflected light) in the investigated aquatic insects. Thus, horizontally polarizing artificial lamplit surfaces can function as an effective ecological trap due to this synergism of optical cues, especially in the urban environment.

Diel flight behaviour and dispersal patterns of aquatic Coleoptera and Heteroptera species with special emphasis on the importance of seasons

Dispersal flight is the most important and almost the only way for primary aquatic insects to find new water habitats. During a 30-week-long project, we monitored the flight dispersal behaviour of aquatic beetles and bugs with using highly and horizontally polarizing agricultural black plastic sheets laid onto the ground. Based on the flight data of more than 45,000 individuals and 92 species, we explored and described eight different diel flight activity patterns. We found that seven of eight dispersal patterns are consistent with the previous knowledge, while three conspicuous mass dispersal periods can be identified as in the mid morning and/or around noon and/or at nightfall. As an exception, we found a ‘daytime’ pattern occurred exclusively in spring, in which mass dispersal can be seen from mid morning to late afternoon. In contrast to previous studies, we emphasize here that the seasonality has to be considered in evaluation of the diurnal flight activity. According to the seasons, a ‘three code sign’ was proposed to indicate the diel dispersal flight behaviour of a species for a year. Most of the species utilize different diel activity patterns in different seasons. In spring, the daytime pattern was the preferred type, but in summer and autumn, the evening types were the most popular patterns. We stated that the seasonal change of air temperature has a crucial role in that a pattern could be manifested in a given season or not and brings a need to change the diel dispersal pattern among seasons.

Seasonal and diel dispersal activity characteristics of Sigara lateralis (Leach, 1817) (Heteroptera: Corixidae) with special emphasis on possible environmental factors and breeding state

Both the daily and the seasonal dispersal dynamics of the true water bug, Sigara lateralis (Leach, 1817) were studied in 2000 and 2005 under various environmental circumstances by monitoring the number of individuals attracted to highly and horizontally polarising shiny black plastic sheets laid on the ground. The diel and seasonal dispersal activity characteristics of S. lateralis are described here in detail. The seasonal patterns of mass dispersal of water insects in general were different in the two studied years, the possible reason for which could be that there was a longer period when the environmental factors temporarily influenced the number of flying insects. The diel dispersal patterns of S. lateralis were also different in 2000 and 2005. It seems that the diurnal dispersal pattern of S. lateralis described previously can change year by year. Females outnumbered males in most cases, and females with eggs were the most active during mass dispersal.

Aquatic and semiaquatic Heteroptera (Nepomorpha and Gerromorpha) fauna of Greek holiday islands (Rhodes, Crete and Corfu) with first records of three species from Europe and Greece

A comprehensive survey on aquatic and semiaquatic bugs (Heteroptera: Nepomorpha and Gerromorpha) of three Greek holiday islands, Rhodes, Crete and Corfu, was conducted from 2007 to 2010 at 237 localities. In this paper, hundreds of detailed records for 30 taxa in nine families are given. The occurrences of Rhagovelia infernalis africana Lundblad, 1936 and Velia mariae Tamanini, 1971 are confirmed and recorded for the first time from Europe sensu stricto. Additionally, some notes on morphology, taxonomy and distribution of the European species of Rhagovelia and Velia are also given, Velia mariae is recorded for the first time not only from several Greek islands, but from continental Greece and Bulgaria as well. Gerris asper (Fieber, 1860), a common European species, was also found for the first time in Greece. Furthermore, new occurrence data are given for endemic taxa; Sigara nigrolineata mendax Heiss & Jansson, 1986 and Velia rhadamantha rhadamantha Hoberlandt, 1941 (whose distribution is restricted to Crete and small adjacent islands) are very common throughout Crete, whereas Ilyocoris cimicoides jonicus (Lindberg, 1922) apparently is rare in Corfu.

Seasonal and diel flight activity patterns of aquatic Coleoptera and Heteroptera

1t is a well known fact that most aquatic insects can tly. Data collected by Jight trapping (BENEDEK & JÁSZAI 1972, NovtNSZKY 2003) and field observations are not suitable to analyze daily tlight activity patterns of aquatic insects because the attraction of light traps is considerably reduced by day due to the higher ambient light intensity. At the same time, the seasonal and diurna) tlight patterns have been investigated effectively only severa) times (FERNANDO 1958, PoPHAM 1964, PAJUNEN & JANssoN 1969, FERNANDO & ÜALBRAITH 1973, LANDIN 1980, BEHR 1990, 1993, BODA et al. 2003, CsABAI et al. 2003, 2004,). Aquatic insects recognize aquatic habitats by means ofthe horizontal linear polarization oflight retlected from the water surface (SCHWIND 1991 ). Numerous earlier field experiments (ScHWIND & HoRVÁTH 1993, HoRVÁTH 1995, HoRVÁTH & VARJÚ 1997) have shown that the horizontal polarization of retlected light is the major optical cue that attracts water insects to shiny surfaces; therefore, using horizontal shiny black plastic sheets is a suitable method throughout the day because it always polarizes the retlected light strongly and horizontally (HORVÁTH & VARJÚ 2003). Utilizing this phenomenon of aquatic insects landing on the shiny black plastic foils while foraging for water surfaces, we collected samples over one entire day per week for 2 years. In this paper, only the dispersa) activities of the most abundant species are discussed in detail.

Water striders (Heteroptera: Gerromorpha: Gerridae) of Romania with an update on the distribution of Gerris gibbifer and G. maculatus in southeastern Europe

The Romanian fauna comprises two species of Aquarius Schellenberg, 1800, eight species of Gerris Fabricius, 1794 and one species of Limnoporus Stål, 1868, and we hereby update the distribution and provide insights on the phenology and ecology of all eleven species in this country. We furthermore update the distribution of the two closely related species Gerris gibbifer Schummel, 1832 and G. maculatus Tamanini, 1946 in southeastern Europe. Gerris maculatus is recorded for the first time from Hungary, Montenegro and Slovenia, and the first detailed localities from Romania and Serbia are given. All bibliographic records of G. gibbifer from Romania, Macedonia and Serbia are based on misidentification and this species is thus excluded from the faunal lists of these countries. Both G. gibbifer and G. maculatus occur in Croatia, Hungary, Ukraine, and probably Slovenia.

Livin' on the edge: the importance of adjacent intermittent habitats in maintaining macroinvertebrate diversity of permanent freshwater marsh systems

ABSTRACT Taxonomic and functional patterns of macroinvertebrate communities were investigated to reveal the importance of different habitat units within a marsh system in maintaining its macroinvertebrate diversity. Hydrogeomorphic units based on their functional characteristics were used to distinguish 3 types of aquatic habitats within the marsh system: (1) Core Unit (CU), a permanent inundation of a wetland in the central position of a marsh system; (2) Transitional Unit (TU), a seasonal to intermittent inundation of a wetland, with seasonal saturation; and (3) Satellite Unit (SU), seasonal depression wetlands with ephemeral to intermittent saturation. We hypothesized that communities in each Unit would have specific taxonomic and functional features. Species richness was highest in the TU, with unique community composition in the SU, and moderately high species richness characterized by a stable community with high taxonomic distinctness in the CU. The metacommunity of the entire marsh was nearly random with a substantial equilibrium between beta-diversity features: replacement and dissimilarity. Our results suggest that the combination of directly connected or isolated waterbodies in close proximity to a large core waterbody is likely to maintain the highest level of diversity. Each Unit has unique characteristics and provides habitats for species with different ecological traits; thus, different aquatic habitats of a marsh system should be considered together as one meaningful ecological entity.

Temporal and spatial dynamics in aquatic macroinvertebrate communities along a small urban stream

Urbanization is a current and increasing threat to biodiversity. The effects of urbanization on the functional and taxonomic composition of macroinvertebrate assemblages were investigated in two seasons along a small urban stream. Species composition was determined by the rate of urbanization; however, response of species richness could not be evidenced. Relative abundance of the sensitive macroinvertebrate groups (EPT%) was negatively related to urbanization. Almost all feeding groups showed a sharp decline in the number of specimens along the increase of urbanization. The study supports the view that urbanization has a negative effect on the biological quality of a stream, yet, this obvious impact can be overridden by different measures such as modification in streambed morphology. The altered conditions and new circumstances in urban environments lead to the creation of novel ecosystems, inhabited by macroinvertebrate communities with species richness approaching that of low impacted sites. However, species composition of these communities could be basically different from that of the natural ones.