Diel Flight Activity Research Articles

Seasonal change and influence of environmental variables on host-seeking activity of the biting midge Culicoides sonorensis at a southern California dairy, USA

BackgroundAs a primary vector of bluetongue virus (BTV) in the US, seasonal abundance and diel flight activity of Culicoides sonorensis has been documented, but few studies have examined how time of host-seeking activity is impacted by environmental factors. This knowledge is essential for interpreting surveillance data and modeling pathogen transmission risk.MethodsThe diel host-seeking activity of C. sonorensis was studied on a California dairy over 3 years using a time-segregated trap baited with CO2. The relationship between environmental variables and diel host-seeking activity (start, peak, and duration of activity) of C. sonorensis was evaluated using multiple linear regression. Fisher’s exact test and paired-sample z-test were used to evaluate the seasonal difference and parity difference on diel host-seeking activity.ResultsHost-seeking by C. sonorensis began and reached an activity peak before sunset at a higher frequency during colder months relative to warmer months. The time that host-seeking activity occurred was associated low and high daily temperature as well as wind speed at sunset. Colder temperatures and a greater diurnal temperature range were associated with an earlier peak in host-seeking. Higher wind speeds at sunset were associated with a delayed peak in host-seeking and a shortened duration of host-seeking. Parous midges reached peak host-seeking activity slightly later than nulliparous midges, possibly because of the need for oviposition by gravid females before returning to host-seeking.ConclusionsThis study demonstrates that during colder months C. sonorensis initiates host-seeking and reaches peak host-seeking activity earlier relative to sunset, often even before sunset, compared to warmer months. Therefore, the commonly used UV light-baited traps are ineffective for midge surveillance before sunset. Based on this study, surveillance methods that do not rely on light trapping would provide a more accurate estimate of host-biting risk across seasons. The association of environmental factors to host-seeking shown in this study can be used to improve modeling or prediction of host-seeking activity. This study identified diurnal temperature range as associated with host-seeking activity, suggesting that Culicoides may respond to a rapidly decreasing temperature by shifting to an earlier host-seeking time, though this association needs further study.Graphical

Diel flight activity in response to attractants in the predatory beetle, Cathartus quadricollis (Coleoptera: Silvanidae) in macadamia nut in Hawaii.

The diel flight activity in Cathartus quadricollis (Guerin-Meneville) (Coleoptera: Silvanidae), a predator of two important pests in Hawaii, coffee berry borer, Hypothenemus hampei (Ferrari) and tropical nut borer, Hypothenemus obscurus (F.) (Coleoptera: Curculionidae: Scolytinae) was studied in a macadamia nut orchard using yellow sticky traps baited with pheromone and fungal volatile attractants. The study was conducted at different months throughout the year and at different times during the lunar cycle (new moon and full moon). Flight activity peaked in the late hours of the photophase into the early hours of the scotophase, between 1830 and 2000 h; flight activity also occurred but to a lesser extent in the early morning hours between 0700 and 1030 h. Numbers of captured C. quadricollis during periods of flight activity were negatively correlated with wind speed. The implications of these findings for the development of optimal pest management strategies including biological control are discussed.

Plasmodium relictum infection in Culex quinquefasciatus (Culicidae) decreases diel flight activity but increases peak dusk flight activity

BackgroundParasites are recognized for their ability to modify host physiology and behaviours in ways that increase parasite fitness. Protozoan parasites of the genus Plasmodium are a group of widespread vector-borne parasites of vertebrates, causing disease to a wide range of hosts, but most notably to human and avian hosts.MethodsThe hypothesis that infection with the avian malaria, Plasmodium relictum (GRW4 lineage) impacts flight activity in one of their natural vectors, Culex quinquefasciatus, was tested using both parasites and mosquitoes colonized from local populations in East-Central Texas, USA. Groups of Cx. quinquefasciatus were allowed to feed directly on canaries with active P. relictum infections and control canaries with no P. relictum exposure history. Additionally, how P. relictum sporozoite invasion of mosquito salivary glands impacts mosquito flight activity behaviour was tested using a Locomotor Activity Monitor for both control and infected females. Generalized linear mixed models were used to evaluate the influence of infection status on the response variables of flight activity (continuous) and probability of flight occurring (binomial).ResultsInfection status was a significant predictor of flight activity and flight probability and interactions between infection status and experimental period of infection as well as infection status and dusk were statistically significant predictors of flight activity. Plasmodium relictum infected mosquitoes had a mean flight activity of 3.10 and control mosquitoes had an overall mean flight activity of 3.13.DiscussionBased on these results, avian malaria parasites increase the flight activity of these mosquitoes at hours known for peak host-seeking behaviour but decrease overall diel activity.ConclusionAlthough the ramifications of this behavioural change for P. relictum transmission are unclear, these results provide additional empirical evidence suggesting that avian malaria can influence mosquito behaviour and modulate transmission potential.

Diel flight activity of wild-caught Anopheles farauti (s.s.) and An. hinesorum malaria mosquitoes from northern Queensland, Australia

BackgroundSpecies in the Anopheles farauti complex are major malaria vectors in the Asia Pacific region. Anopheline mosquitoes exhibit circadian and diel rhythms in sugar- and blood-feeding (biting), flight activity, oviposition, and in some species, a short-lived dusk/early night associated swarming behaviour during which mating occurs. A behavioural study of wild-caught mosquitoes from Queensland, Australia was conducted to investigate the differences in diel rhythmic flight activity between two cryptic species in several reproductive states.ResultsThe 24-hour flight activity of individual adult female mosquitoes under light:dark cycle conditions were monitored with a minute-to-minute time resolution using an infrared beam break method. Mosquitoes were analyzed for reproductive state (insemination and parity) and identified to species [An. farauti (s.s.) Laveran and An. hinesorum Schmidt] by PCR analysis. We compared daily total flight activity, timing of activity onset, the peak in early nocturnal activity, and patterns of activity during the scotophase (night). Species-specific differences between An. farauti and An. hinesorum were observed. Compared to An. farauti, An. hinesorum had an earlier onset of dusk activity, an earlier peak in nocturnal activity, and a higher level of activity at the onset of darkness. Small differences between species were also observed in the pattern of the dusk/early-night bouts of activity. A second nocturnal peak in inseminated nulliparous An. hinesorum was also observed during the middle of the scotophase.ConclusionsThe behavioural differences between these two sympatric species of the An. farauti complex might contribute to subtle differences in habitat adaptation, the timing of host-seeking and/or sugar-feeding activity. This study provides baseline data for analysis of populations of mosquitoes from other geographical regions where these species are malaria vectors, such as in the Solomon Islands and Papua New Guinea. This is important as selective pressures due to long-term use of indoor residual spraying of insecticides and insecticide-treated bed nets are shifting the nocturnal profile of biting behaviour of these vectors to earlier in the night.

QTL Determining Diel Flight Activity in Male Culex pipiens Mosquitoes.

Members of the Culex pipiens complex differ in physiological traits that facilitate their survival in diverse environments. Assortative mating within the complex occurs in some regions where autogenous (the ability to lay a batch of eggs without a blood meal) and anautogenous populations are sympatric, and differences in mating behaviors may be involved. For example, anautogenous populations mate in flight/swarms, while autogenous populations often mate at rest. Here, we characterized flight activity of males and found that anautogenous strain males were crepuscular, while autogenous strain males were crepuscular and nocturnal, with earlier activity onset times. We conducted quantitative trait locus (QTL) mapping to explore the genetic basis of circadian chronotype (crepuscular vs. crepuscular and nocturnal) and time of activity onset. One major-effect QTL was identified for chronotype, while 3 QTLs were identified for activity onset. The highest logarithm of the odds (LOD) score for the chronotype QTL coincides with a chromosome 3 marker that contains a 15-nucleotide indel within the coding region of the canonical clock gene, cryptochrome 2. Sequencing of this locus in 7 different strains showed that the C-terminus of CRY2 in the autogenous forms contain deletions not found in the anautogenous forms. Consequently, we monitored activity in constant darkness and found males from the anautogenous strain exhibited free running periods of ~24 h while those from the autogenous strain were ~22 h. This study provides novel insights into the genetic basis of flight behaviors that likely reflect adaptation to their distinct ecological niches.

Diel flight pattern and size‐dependent flight speed of kudzu bug, Megacopta cribraria (Fabricius)

AbstractKudzu bug, Megacopta cribraria (Fabricius) (Hemiptera: Plataspidae), was introduced to North America in 2009 and has since spread across the eastern and south‐eastern United States, where it poses an economic threat to leguminous crop production, especially soya bean. However, we still lack an understanding of many basic aspects of their flight‐related biology, including descriptions of their pattern of diel flight activity, their dispersal capacity and the determinants of each. Using cross‐vane bucket traps and flight mills, we found that kudzu bug exhibits a diel flight activity pattern in the field that is well characterized by temperature and a quadratic relationship with time of day. In general, the number of adults collected in the cross‐vane bucket traps rose from 07:30 and declined from 17:30 to 19:30. No kudzu bugs were collected before 07:30 or after 19:30 during any of the replicates. We also demonstrate on flight mills that females fly faster than males, and that this difference is due to differences in their size. These basic biological findings may help to inform management decisions and improve our understanding of the invasion dynamics of M. cribraria.

Diel Flight Activity Patterns of the Red Palm Weevil (Coleoptera: Curculionidae) as Monitored by Smart Traps

The red palm weevil, Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae), is a serious pest of palm in many subtropical and tropical regions of the world. Traps baited with aggregation pheromones are important management tools used to control this weevil. The daily flight activ ity patterns of the red palm weevil in Saudi Arabian date palm orchards were observed using smart traps (STs) with a catch period of 3 h (8 periods daily). Conventional bucket traps (CTs) were used for comparison. The capture efficiency of the STs was not significantly different from that of the CTs. A circular statistics analysis showed that the time of adult capture in the STs was nonrandom and indicated mainly diurnal activity; few adults were captured at night. The STs revealed differential activity between the sexes. The female activity pattern exhibited 2 strong peaks at 7 to 9 AM and 4 to 7 PM, and the 2nd peak was significantly higher than the 1st peak. The male activity pattern showed 3 peaks at 7 to 10 AM, 1 to 4 PM, and 4 to 7 PM with no significant differences among the peaks. Males initiated activity before the females. The number of adults captured by STs was positively cor related with the time of sunrise and wind velocity, negatively correlated with the time of sunset and the ambient temperature, and not significantly correlated with the relative humidity. Although these patterns were consistent during the study period, they differed from a variety of other patterns reported in European and Southern Asian environments, which suggests that R. ferrugineus has evolved considerable behavioral flexibility in coping with harsh environmental conditions typical of hot arid date production areas in Saudi Arabia. Knowledge of R. ferrugineus daily activity patterns in local field environments can help managers optimize the timing of pesticide applications and other control activities.

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.

Species Turnover and Diel Flight Activity of Species of Dung Beetles,Onthophagus, in the Tropical Lowland Forest of Peninsular Thailand

Species turnover and temporal variation of forest insects were used to explain the ecological succession and ecological segregation between efficiently competing species. In this study, species richness, abundance, and beta-diversity of the genus Onthophagus (Coleoptera: Scarabaeidae) assemblages between 2003 and 2007 were described and the diel—flight activity was examined in the disturbed forest and the interior forest of the lowland tropical rain forest at Ton Nga Chang Wildlife Sanctuary in peninsular Thailand. A total of 2,260 individuals of 22 species in 2003 and 2,382 individuals of 24 species in 2007 were collected. Although species richness and abundance did not differ significantly between the two years, all similarity indices were significantly different. The community structure of Onthophagus assemblage in 2003 demonstrated a heterogeneous pattern, whereas there was a tendency for the pattern to shift toward a more homogeneous structure in 2007. The temporal variation showed two distinct diel—flight activities; diurnal and crepuscular patterns. Six species were crepuscular (O. deflexicollis Lansberge, O. orientalis Harold, O. rudis Sharp, O. sp 1, O. sp 2, and O. sp 4), whereas most of Onthophagus species demonstrated diurnal pattern. Remarkably, five species (O. taurinus White, O. pilularius Lansberge, O. punneeae Masumoto, O. laevis Harold, and O. sp 3.) could not be classified as either diurnal or crepuscular species. It was suggested that the species turnover was probably influenced by the recovery of the forest structure and the decrease of anthropogenic disturbance. Resource partitioning was suggested to be a key factor for crepuscular adaptation in Onthophagus species.

Diel Patterns of Female Host Seeking, Male Swarming, and Sugar Feeding in Fannia conspicua (Diptera: Muscidae) in Southern California

Adult Fannia conspicua Malloch were captured by sweep net at a southern California coastal mountain community to determine diel flight activity and crop/gut sugar (gut sugar) concentration. Male swarming activity was monitored by visual estimation of swarm numbers. Gut sugar content of captured flies was determined by cold anthrone assay. Peak host seeking by female flies generally occurred in early morning (0700-0800) and early evening (1900-2000). Variation in female host-seeking activity was significantly explained by the time elapsed since sunrise or time remaining until sunset, with temperature, humidity, and wind speed having small, but significant effects on activity. Male swarming activity occurred more generally throughout the day, with peaks in mid-morning and mid-afternoon and reduced swarming during periods of highest female host-seeking activity. Male swarming behaviors were only minimally explained by environmental variables. Flies of both sexes commonly fed on fructose sugars with 99.94% of host-seeking female flies (n = 1,647), and 98.93% of swarming male flies (n = 1,398) with gut sugar levels exceeding those of starved flies. Host-seeking female flies had significantly higher overall sugar content than swarming male flies. Male flies had peak gut sugar levels at 0800-0900 and 2000. Female flies had broad peaks in gut sugar level from 0700 to 1200 and 1600 to 1900. Stepwise regression showed that variation in gut sugar level was poorly explained by environmental variables for both sexes.

Biological Parameters ofScirtothrips dorsalis(Thysanoptera: Thripidae) on Selected Hosts

Since its establishment in Florida in 2005, Scirtothrips dorsalis Hood, a highly polyphagous species, has become an economically important pest of ornamental plants and a potentially significant pest of vegetable and fruit crops. Fruit and vegetable production in Florida is trending toward significant adoption of organic methods and use of widely dispersed small fields in rapidly urbanizing landscapes. Landscape plants may serve as refugia from which S. dorsalis recruits can disperse to nearby fruit and vegetable plantings. Therefore, information on this pest's biology including how it is affected by various host species is needed to develop effective integrated pest management (IPM) programs. In the greenhouse and laboratory condition, we studied the effects of various host plants, development, diel flight activity, oviposition, and demographics of S. dorsalis. The pest preferred Jalapeño pepper and Knockout rose over the other hosts, and it was most active between 1000 and 1600 hours EST. Irrespective of the host species, the duration of each of the immature stadia varied within a narrow range, and their respective sizes were quite similar. Demographic parameters quantified included gross reproduction rate (GRR), net reproductive rate (R(o)), intrinsic rate of increase per day (R(m)), finite rate of increase per day (λ), and mean generation time (T). The pest population may increase by a factor of ≈ 1.09/d, so that it may double in 8 or 9 d. The above information should be helpful in the development of sound programs to manage S. dorsalis on various crops and in the formulation of detection strategies by quarantine officers.

Seasonal and diel flight activity patterns of aquatic Coleoptera and Heteroptera

Seasonal and diel flight activity patterns of aquatic Coleoptera and Heteroptera

Diel Flight Pattern and Flight Performance of Cactoblastis cactorum (Lepidoptera: Pyralidae) Measured on a Flight Mill: Influence of Age, Gender, Mating Status, and Body Size

Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) is an invasive herbivore that poses a serious risk to Opuntia cacti in North America. Knowledge of the flight behavior of the cactus moth is crucial for a better understanding of natural dispersal, and for both monitoring and control. We used computer-linked flight mills to investigate diel flight activity and flight performance in relation to gender, age, mating status, and body size. Maximal flight activity for both mated and unmated moths occurred during twilight, whereas flight activity was low during photophase. The total distance flown and the number of initiated flights within a diel cycle were higher in both unmated and mated females than in males, but the longest single flight was similar in both genders. These findings suggest that pheromone trap captures of males likely indicate the simultaneous presence of females and that mated females might even be in areas where males are not detected yet. Flight performance heterogeneity was large, with a small portion of the population (both males and females) performing long unbroken flights, whereas the majority made short flights. Females had higher pupal and adult body size and shorter longevity than males. A few individuals, particularly young mated females, flying long distances may be important for active spread of a population and the colonization of new habitats. Implications of this study in the control of the cactus moth by using the sterile insect technique are discussed.

Diel Flight Pattern and Flight Performance of <I>Cactoblastis cactorum</I> (Lepidoptera: Pyralidae) Measured on a Flight Mill: Influence of Age, Gender, Mating Status, and Body Size

Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) is an invasive herbivore that poses a serious risk to Opuntia cacti in North America. Knowledge of the flight behavior of the cactus moth is crucial for a better understanding of natural dispersal, and for both monitoring and control. We used computer-linked flight mills to investigate diel flight activity and flight performance in relation to gender, age, mating status, and body size. Maximal flight activity for both mated and unmated moths occurred during twilight, whereas flight activity was low during photophase. The total distance flown and the number of initiated flights within a diel cycle were higher in both unmated and mated females than in males, but the longest single flight was similar in both genders. These findings suggest that pheromone trap captures of males likely indicate the simultaneous presence of females and that mated females might even be in areas where males are not detected yet. Flight performance heterogeneity was large, with a small portion of the population (both males and females) performing long unbroken flights, whereas the majority made short flights. Females had higher pupal and adult body size and shorter longevity than males. A few individuals, particularly young mated females, flying long distances may be important for active spread of a population and the colonization of new habitats. Implications of this study in the control of the cactus moth by using the sterile insect technique are discussed.

A ‘polarisation sun‐dial’ dictates the optimal time of day for dispersal by flying aquatic insects

Summary1. Daily changes in the flight activity of aquatic insects have been investigated in only a few water beetles and bugs. The diel flight periodicity of aquatic insects and the environmental factors governing it are poorly understood.2. We found that primary aquatic insects belonging to 99 taxa (78 Coleoptera, 21 Heteroptera) fly predominantly in mid‐morning, and/or around noon and/or at nightfall. There appears to be at least four different types of diurnal flight activity rhythm in aquatic insects, characterised by peak(s): (i) in mid‐morning; (ii) in the evening; (iii) both in mid‐morning and the evening; (iv) around noon and again in the evening. These activity maxima are quite general and cannot be explained exclusively by daily fluctuations of air temperature, humidity, wind speed and risks of predation, which are all somewhat stochastic.3. We found experimental evidence that the proportion (%) P(θ) of reflecting surfaces detectable polarotactically as ‘water’ is always maximal at the lowest (dawn and dusk) and highest (noon) angles of solar elevation (θ) for dark reflectors while P(θ) is maximal at dawn and dusk (low solar elevations) for bright reflectors under clear or partly cloudy skies.4. From the temporal coincidence between peaks in the diel flight activity of primary aquatic insects and the polarotactic detectability P(θ) of water surfaces we conclude that the optimal times of day for aquatic insects to disperse are the periods of low and high solar elevations θ. The θ‐dependent reflection–polarisation patterns, combined with an appropriate air temperature, clearly explain why polarotactic aquatic insects disperse to new habitats in mid‐morning, and/or around noon and/or at dusk. We call this phenomenon the ‘polarisation sun‐dial’ of dispersing aquatic insects.

Diel flight activity and ecological segregation within an assemblage of tropical forest dung and carrion beetles

Temporal variation in activity of dung and carrion beetles in tropical forest is considered as a mechanism of ecological segregation between potentially competing species. We describe the diel flight activity of Scarabaeidae collected with baited pitfall traps at Les Nouragues field station in French Guiana. A total of 2663 individuals of 63 species was recorded, from the subfamilies Coprinae, Scarabaeinae and Aphodinae. Temporal guilds of diurnal, nocturnal and crepuscular species were identified. Diurnal species were about twice as numerous and abundant as either nocturnal or crepuscular species. Two main activity patterns characterize the diurnal species while nocturnal and crepuscular species show overlapping activity. The association of activity rhythm with the other niche variables, food selection, functional group, body size and relative abundance, was analysed using multiple correspondence analysis. Small diurnal coprophagous species were opposed to large crepuscular necrophagous species. Species packing is suggested but further analysis showed that the variables were independent of one another. The temporal differentiation of species combined with separation along multiple niche dimensions and resource gradients may facilitate the coexistence of species assumed to be strongly affected by interspecific competition.

Auditory Sensitivity and Diel Flight Activity In Neotropical Lepidoptera

If the primary function of ultrasound-sensitive ears in Lepidoptera is to detect the echolocation calls of insectivorous bats, diurnal species should exhibit signs of ultrasonic deafness. To test this hypothesis we recorded the 24-h (diel) flight activity of a sample of Neotropical butterflies and moths, including members of the Dioptinae, a reportedly diurnal moth subfamily. All of the butterflies examined were exclusively diurnal and we suggest that these insects are day-locked because they lack the ultrasound-sensitive ears that permit nocturnal taxa to co-exist with bats. Nondioptine moths possess sensitive, bat-tuned ears and exhibit levels of nocturnal flight ranging from complete to mixed day/night activity. Dioptine moths are significantly less nocturnal and significantly deafer than nondioptines and exhibit flight activity patterns ranging from completely diurnal to completely nocturnal. We suggest that diurnality in the Dioptinae is an apomorphic trait that has resulted in a loss of auditory sensitivity in some species but that others may retain functional ears depending on their levels of nocturnality and consequent exposure to bats.

Temperature and Diel Catches of Trialeurodes vaporariorum and Bemisia tabaci (Homoptera: Aleyrodidae) Adults on Sticky Traps in the Greenhouse

Patterns of diel flight activity of the greenhouse whitefly, Trialeurodes vaporariorum (Westwood), and sweetpotato whitefly, Bemisia tabaci (Gennadius), were investigated on poinsettia, Euphorbia pulcherrima Willd., and gerbera daisy, Gerbera jamesonii H. Bolus, under greenhouse and environmentally controlled conditions. Adult flight activity was monitored at 2-h intervals (from 0700 to 2100 h EST) at various heights using yellow sticky traps. Traps placed 5 cm above the top of the plant canopy caught more adults of both species than traps placed higher. The daily patterns of catches of T. vaporariorum and B. tabaci adults in the greenhouse were similar and were unimodal with peak catches occurring between 0900–1300 h. Numbers of adults caught on the sticky traps in the greenhouse were correlated with temperature and relative humidity for T. vaporariorum, but not for B. tabaci. Few adults were caught during the dark hours (from 2100 to 0700 h). Under constant temperatures of 20°, 25°, and 30°C, the flight activity patterns of both whitefly species were unimodal, with peak catches of T. vaporariorum and B. tabaci occurring in the morning and afternoon, respectively. Differences in temperature did not significantly alter the pattern of catches of adults on sticky traps. The lowest temperature for initiation of whitefly flight was 16–17°C for T. vaporariorum, and 17–18°C for B. tabaci.

Composition, structure, and competitive behaviour in a guild of Ecuadorian rain forest dung beetles (Coleoptera; Scarabaeidae)

A guild of neotropical rain forest dung scarabs, collected by baited pit traps, was composed of 11 genera and 31 species of Scarabaeinae. Relative abundances were highly equitable. Population densities were high and stable through the transition from wet to dry season. Competition for dung was intense and removal and burial rates were rapid. Resource use differed between genera and species in diel flight activity, foraging and dung removal methods, and behavior. Interspecific aggression and dung stealing behaviors were well developed. Reproductive activity was inversely correlated with aggression and parental investment.

Diel and Seasonal Patterns of Flight Activity of Ceratopogonidae in Northeastern Colorado: Culicoides 123

Diel and seasonal patterns of flight activity of Culicoides variipennis (Coquillett), C. crepuscularis Malloch, C. hieroglyphicus Malloch, and C. palmerae James (Diptera: Ceratopogonidae) were studied in northeastern Colorado. Culicoides variipennis was active Mar.–Nov., flying in the late afternoon in Mar., Apr., and Nov., throughout the diel pehod in May, June, Sept., and Oct., and during scotophase in July and Aug. Diel activity was greatest near sunset but sometimes increased near sunrise. Flight activity also increased during periods of moonlight. Flight was not observed at temp < 7° or > 35°C. Culicoides crepuscularis was active May–Nov. Diel flight activity was greatest immediately after sunset, diminished during late scotophase, but increased occasionally near sunrise or during early photophase. Numbers of C. crepuscularis males in flight increased during periods of moonlight. Culicoides hieroglyphicus and C. palmerae were active Apr.–Oct. and May–June, respectively. Patterns of flight activity of both species were apparently a modal, but the greatest numbers were collected in the afternoon in June.