Circadian rhythms of insect pheromone titer, calling, emission, and response: a review.

Many insect species have circadian rhythms of pheromone production/titer, calling, emission, and response that are involved in intraspecific communication and impact pest management practices. Rhythms of pheromone biosynthesis, most studied in moths affecting forestry and agriculture, contribute to a periodicity of pheromone concentration or titer within glands or hemolymph. Calling rhythms by the pheromone-emitting sex are physical movements (pumping, vibrating wings) that aid in release and dispersion of the volatile pheromone components attractive to the opposite conspecific sex or both sexes. Circadian rhythms of emission of pheromone also occur as a result of an interaction between calling and the titer of pheromone available for release. Responding individuals usually show a coincidental rhythm of dispersal flight while seeking pheromone plumes in which, by orienting upwind, the insects find mates or food resources. However, some species begin searching an hour or more before the emitting sex initiates calling and emission, which benefits mass trapping control programs because the baited traps do not compete initially with natural pheromone sources. In our review, data of daily rhythms of moths and other insects were extracted from the literature by screen capture software to calculate mean time of activity and standard deviation and fit to normal curves. These methods are illustrated for various insects and as a basis for discussion of interactions of pheromonal circadian rhythms of the well-studied gypsy moth Lymantria dispar, spruce budworm moth Choristoneura fumiferana, turnip moth Agrotis segetum, and cabbage looper moth Trichoplusia ni. The various circadian rhythms are discussed in relation to application of species-specific sex and aggregation pheromones for benign biological control and management of pest insects.

Effects of the colour of photophase light on locomotor activity in a nocturnal and a diurnal South African rodent.

Many physiological and behavioural responses to varying qualities of light, particularly during the night (scotophase), have been well documented in rodents. We used varying wavelengths of day-time (photophase) lighting to assess daily responses in locomotor activity in the nocturnal Namaqua rock mouse (Micaelamys namaquensis) and diurnal four-striped field mouse (Rhabdomys pumilio). Animals were exposed to three light-dark cycle regimes: a short-wavelength- (SWLC, blue), a medium-wavelength- (MWLC, green) and a long-wavelength light-dark cycle (LWLC, red). Overall, daily locomotor activity of both species changed according to different wavelengths of light: the diurnal species displayed most activity under the SWLC and the nocturnal species exhibited the highest levels of activity under the LWLC. Both species showed an increase in diurnal activity and a decrease in nocturnal activity under the LWLC. These results indicate an attenuated responsiveness to long-wavelength light in the nocturnal species, but this does not appear to be true for the diurnal species. These results emphasize that the effect of light on the locomotor activity of animals depends on both the properties of the light and the temporal organization of activity of a species.

Daily rhythms of rectal and body surface temperatures in donkeys during the cold-dry (harmattan) and hot-dry seasons in a tropical savannah.

The aim of the study was to evaluate daily rhythms of rectal temperature (RT) and body surface temperature (BST) of adult, yearling and foal donkeys during the cold-dry (harmattan) and hot-dry seasons in a tropical savanna. The RTs and BSTs of 30 clinically healthy, free-ranging donkeys were recorded using digital and infrared thermometers. The RT and BST of each donkey and thermal environmental parameters inside the pen were measured bi-hourly from 0600 to 0600 hours (GM + 1) on each experimental day. Application of single cosinor procedure showed that RT and BST exhibited varying levels of daily rhythmicity in both seasons, with values usually higher during the afternoon periods of the photophase of the light/dark cycle. The oscillatory pattern differed with season, with greater amplitude recorded during the cold-dry season than the hot-dry season. The acrophases of the RT and BST were mostly restricted to the photophase of the light/dark cycle in both seasons. The mean values of RT in the adult (37.10 ± 0.10 °C), yearling (37.19 ± 0.10 °C) and foal (37.45 ± 0.11 °C) donkeys were higher (F = 93.41, P < 0.0001) during the hot-dry season than the cold-dry season (35.40 ± 0.05 °C, 35.50 ± 0.04 °C and 36.20 ± 0.05 °C, respectively). In conclusion, seasonal changes influenced significantly the daily rhythmicity of RT and BST in donkeys, kept under natural light/dark cycle.

Biological characteristics of Grapholita molesta (Lepidoptera: Tortricidae) induced to diapause in laboratory.

In southern Brazil, Grapholita molesta (Busck) (Lepidoptera: Tortricidae) uses diapause as survival strategy during the winter (May-August). In our study, we evaluated the effect of diapause on biological characteristics of the species for 4 months in laboratory. Newly hatched larvae of G. molesta were induced to diapause changing the photoperiod and temperature (T) (12 ± 1°C), relative humidity (RH) (70 ± 10%), and a photophase of 12 h and, when they started diapause in the prepupal stage, the conditions were kept for 4 months. Afterwards, the insects were induced to finalize the diapause process at T 25 ± 1°C, RH 70 ± 10%, and a photophase of 16 h. We evaluated the duration and viability of the larval stages and pupae, pupae weight at 24 h and sex ratio (sr), periods of preoviposition, oviposition, and postoviposition; adult life span (males and females); fecundity (daily and total); embryonic period duration and eggs viability, comparing the data with insects nondiapause. The results show that diapause greatly affected the viability of pupal-adult stages of the population (21.8%) when compared with insects' nondiapause (80.0%). Total fecundity (83.0 eggs) and mean life span (12.0 d) of insects diapause was significantly lower compared with insects nondiapause (173.0 and 17.0), respectively. However, these differences were not observed in the sr, which was similar to insects diapause (sr = 0.41) and insects nondiapause (sr = 0.49). The diapause induced for 4 months negatively affects reproduction and life span of adults of G. molesta.

Physiological rhythms are influenced by photophase wavelength in a nocturnal and a diurnal rodent species from South Africa.

The quality and quantity of light changes significantly over the course of the day. The effect of light intensity on physiological and behavioural responses of animals has been well documented, particularly during the scotophase, but the effect of the wavelength of light, particularly during the photophase, less so. We assessed the daily responses in urine production, urinary 6-sulfatoxymelatonin (6-SMT) and glucocorticoid metabolite (uGCM) concentrations in the nocturnal Namaqua rock mouse (Micaelamys namaquensis) and diurnal four striped field mouse (Rhabdomys pumilio) under varying wavelengths of near monochromatic photophase (daytime) lighting. Animals were exposed to a short-wavelength light cycle (SWLC; ∼465-470 nm), a medium-wavelength light cycle (MWLC; ∼515-520 nm) and a long-wavelength light cycle (LWLC; ∼625-630 nm). The SWLC significantly attenuated mean daily urine production rates and the mean daily levels of urinary 6-SMT and of uGCM were inversely correlated with wavelength in both species. The presence of the SWLC greatly augmented overall daily 6-SMT levels, and simultaneously led to the highest uGCM concentrations in both species. In M. namaquensis, the urine production rate and urinary 6-SMT concentrations were significantly higher during the scotophase compared to the photophase under the SWLC and MWLC, whereas the uGCM concentrations were significantly higher during the scotophase under all WLCs. In R. pumilio, the urine production rate and uGCM were significantly higher during the scotophase of the SWLC, not the MWLC and LWLC. Our results illustrate that wavelength in the photophase plays a central role in the entrainment of rhythms in diurnal and nocturnal African rodent species.

Aphids-induced plant volatiles affect diel foraging behavior of a ladybird beetle Coccinella septempunctata.

The ladybird beetle Coccinella septempunctata (L.) is an important biocontrol agent of pests such as various aphid species. Despite being one of the most studied coccinellid species, many aspects of its foraging behavior are still not completely understood. This study focuses on the diel foraging behavior of C. septempunctata, investigating their olfactory orientation toward aphid-infested plants, walking activity on plants and on the soil, and feeding rates. In the scotophase the ladybird beetles were significantly more attracted to the odor of aphid-infested plants, on which they also showed considerably higher walking activity then on uninfested controls. Females were more prone to utilize olfactory cues when searching for prey and fed at higher rates than males; this shows that they are better adapted to nocturnal activity, as they require higher food intake. Coccinella septempunctata have the same feeding rate during the scotophase as in the photophase. Our study shows that C. septempunctata has the potential to forage in the scotophase if prey is abundant. The results support the hypothesis that volatiles of aphid-infested plants can attract or arrest foraging adult ladybird beetles, even in the darkness, which makes a considerable contribution to efficient prey search and enhances feeding capacity.

The Effect of Photoperiods and Light Intensity on Mating Behavior and Reproduction of Grapholita molesta (Lepidoptera: Tortricidae).

Oriental fruit moth, Grapholita molesta (Busck), is a worldwide pest and is the dominant pest of rosaceous plants in northern China. Little is known, however, about the influence of abiotic factors on the daily life history events of this economically important pest, so here we evaluated the effect of different photoperiods (L:D) (0:24; 2:22; 4:20; 6:18; 8:16; 10:14; 12:12; 14:10; 15:9 [control]; 16:8; 18:6; 20:4; 22:2; and 24:0 h) and light intensities (50, 100, 200, 300, 400, and 500 lux) on the mating behavior and reproduction of oriental fruit moth. We found that oriental fruit moth adults with an 8, 9, or 10 h scotophase showed considerably more courtship behavior than those in other photoperiod treatments. Meanwhile, male fanning and male 'crawling in a circle' behaviors significantly decreased with increasing light intensity. Neither female or male oriental fruit moth longevity nor the egg hatch rate were influenced by photoperiod (P = 0.146; 0.271; 0.107) or light intensity (P = 0.268; 0.08; 0.123). In both photoperiod and light intensity treatments (P < 0.05), the number of eggs laid daily by females was significantly influenced by female age, decreasing with greater age. Female oriental fruit moth lifetime fecundity was influenced by photoperiod, with the 9, 10, 16, 18, and 22 h scotophase periods having higher fecundity than other treatments. Meanwhile, fecundity decreased with increasing light intensity.

Photoperiod Differences in Sand Fly (Diptera: Psychodidae) Species Richness and Abundance in Caves in Minas Gerais State, Brazil.

Caves are unique habitats that are inhabited by a diverse and singular biota. Among these inhabitants are sand flies, which are of great epidemiological interest in the Neotropical region because they are vectors of Leishmania The period of activity of these insects is usually crepuscular and nocturnal, but there are reports of diurnal activity of sand flies in caves. Thus, the aim of this study was to evaluate the periodicity of daily activity of sand flies in cave environments in the municipality of Pains, Minas Gerais. Sand flies were collected with light traps, which were operated for 5 consecutive days in the rainy season and in the dry season. Samples were collected every 12 h and separated between photophase and scotophase periods. In total, 1,777 sand flies of 23 species were collected. The most abundant species was Lutzomyia renei (Martins, Falcão, and Silva) (44%), followed by Lutzomyia longipalpis (Lutz and Neiva) (15%), Evandromyia edwardsi (Mangabeira) (11%), and Micropygomyia quinquefer (Costa Lima) (6%). The richness and abundance of total sand flies and the abundance of male and female sand flies in the aphotic zone of the caves did not differ between the photophase and scotophase, but differed between photoperiods at the entrance and at sites surrounding the caves. From our study of the daily activity of these insects in this ecotope, it will be possible to know which period of the day is of greatest risk of exposure of vertebrates who visit or live in these environments, including the human population.

Oviposition by Female Plodia interpunctella (Lepidoptera: Pyralidae): Description and Time Budget Analysis of Behaviors in Laboratory Studies.

The oviposition behavior of the Indian meal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), a major insect pest of durable stored foods, was studied in small experimental arenas under laboratory conditions using videography, and a time budget analysis of its behaviors was documented. Resting gravid females typically became active shortly after the start of the scotophase. The characteristic behaviors exhibited by mated females prior to oviposition included antennal movement, grooming of antennae and mouth parts using the forelegs, walking or flying, and abdomen bending and dragging. Pre-oviposition behaviors such as antennal grooming and walking or flying were observed to alternate several times before females commenced the abdominal dragging behavior that preceded egg laying. Eggs were laid singly or sometimes in groups, either freely or stuck to food material. Gravid females showed little or no movement during the photophase; however, they actively flew and oviposited during the scotophase. Females allocated only a small portion of their time to oviposition while the rest of the time was spent away from food. Females oviposited on food material by making repeated visits, predominantly during the first four hours of the scotophase. Visits and time spent on food declined as the scotophase advanced.

Intermittent lighting programs for layers with different photophases in the beginning of the laying phase / Programas de iluminação intermitentes para poedeiras com diferentes fotofases ao início da fase de postura

ABSTRACT: It was possible to evaluate the effect of continuous and intermittent lighting programs with different photophases on the performance and eggs quality of laying hens, applied to the beginning of the laying phase. The authors used 420 Hy-line Brown laying hens with 21 weeks of age, bred on bedding and submitted for six periods of 28 days between the solstice of summer and winter. The three lighting programs were: (PIC) 16 hours of continuos light, intermittent program with initial and final photophases of 15 minutes (PII15) and an intermittent program with initial and final photophases of 30 minutes (PII30). A completely randomized design with ten repetitions of 14 birds was used. The mean values were subjected analysis of variance and analyzed by the Tukey test (5%). The PIC program showed higher feed intake and eggs' mass about the PII15, and the eggs production of birds, in the PIC, was 1.8% greater than the intermittent photoperiods. Programs of light did not change the egg quality. The intermittent programs for semi-heavy laying hens bred on bedding in an open shed, applied at the beginning of the laying phase, reduced the productive performance of the birds without affecting the eggs quality.

RESUMO: Avaliou-se o efeito de programas de iluminação contínuo e intermitentes com diferentes fotofases sobre o desempenho produtivo e a qualidade de ovos de poedeiras aplicados ao início da fase de postura. Foram utilizadas 420 poedeiras da linhagem Hy line Brown com 21 semanas de idade, criadas sobre cama, submetidas durante seis períodos de 28 dias, entre o solstício de verão e de inverno, a três programas de iluminação: contínuo (PIC) de 16h de luz; programa intermitente com fotofases inicial e final de 15min (PII15); e programa intermitente com fotofases inicial e final de 30min (PII30). Utilizou-se um delineamento inteiramente casualisado, com dez repetições de 14 aves. Os resultados das médias foram submetidos à análise de variância e analisadas pelo teste de Tukey (5%). O programa PIC apresentou maior consumo de ração e massa de ovos em relação ao PII15, a produção de ovos das aves no PIC foi 1,8% superior aos fotoperíodos intermitentes. Os programas de luz não alteraram a qualidade de ovo. Programas intermitentes para poedeiras semipesadas, criadas sobre cama em galpão aberto, aplicados no início da fase de postura reduzem o desempenho produtivo das aves sem afetar a qualidade de ovos.

Diapause initiation and alterations in the life cycle of Grapholita molesta (Busck) (Lepidoptera: Tortricidae) as induced by photoperiodic conditions

Grapholita molesta (Busck) is one of the major pests of Rosaceae, causing significant damage to buds and fruits. In Southern Brazil, its population density is reduced during Rosaceae dormancy months. The present study evaluated the influence of different photoperiods (L:D) (10:14, 11:13, 12:12, 13:11, 14:10 and 16:8) at 25 ± 1ºC and 60 ± 10 percent RH on diapause induction of G. molesta eggs, larvae, prepupae, and pupae. The effects of the photoperiod on the life cycle of non-diapausing insects and on the second generation were also assessed. Prepupal diapause was observed only when eggs and neonates (< 12h-old larvae) were exposed to photophases from 10h to 14h long. Development of non-diapausing individuals and those from the second generation tended to be longer in photophases between 10h and 14h long.

Influência do fotoperíodo no desenvolvimento e na reprodução de Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae) / Influence of the photoperiod on development and reproduction of Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae)

O conhecimento da influência de fatores abióticos sobre os aspectos bioecológicos dos crisopídeos, especialmente das espécies sul-americanas, é importante para a correta utilização desses predadores em programas de controle biológico. Esta pesquisa foi realizada com o objetivo de estudar, em laboratório, aspectos biológicos do predador Chrysoperla externa (Hagen) em diferentes condições fotoperiódicas (8L:16E, 10L:14E, 12L:12E, 14L:10E e 16L:8E), com luminosidade de aproximadamente 1.500 lux, temperatura de 25 ± 2°C e UR de 70 ± 10 por cento. O número de horas-luz não afetou a duração do período embrionário, o número, a duração e a viabilidade dos ínstares, bem como a mortalidade do adulto e o período de pré-oviposição. A duração das fases larval, pré-pupal e pupal diminuiu em função do aumento da fotofase. A viabilidade de ovos foi menor com 10h (85,6 por cento) e 14h (77,8 por cento) de luz. Observou-se uma relação inversa entre a duração da fotofase e a fecundidade, obtendo-se 778,3 ovos por fêmea a 8h de luz e de 233,0 ovos por fêmea a 16h. Não se constataram mudanças morfológicas, fisiológicas ou comportamentais que caracterizassem um sintoma de diapausa em C. externa. Esses resultados fornecem subsídios para o conhecimento do fotoperíodo ideal, visando melhorar as técnicas de criação dessa espécie em laboratório.

To know the influence of abiotic factors on bioecology of Chrysopidae, especially those from South America, is important in order to use these predators in biological control programs. This research was carried out with the objective of studying, in laboratory conditions, the influence of the photoperiods 8L:16D, 10L:14D, 12L:12D, 14L:10D and 16L:8D on biological aspects of Chrysoperla externa (Hagen), with light intensity near to 1,500 lux, temperature of 25 ± 2°C and 70 ± 10 percent RH. The quantity of light did not affect the duration of the embryonic period, the number, duration and viability of instars, as well as adult mortality and pre-oviposition period. However, duration time of the larvae, pre-pupae and pupae decreased with the increase of the photofase. The eggs survival was smaller at 10h (85.6 percent) and 14h (77.8 percent) light. An inverse relationship was observed between photofase duration and fecundity, thus obtaining 778.3 eggs per female maintained at 8h light, and 233.0 eggs per female at 16h light. No morphological, physiological or behavioural changes were observed that could characterize a diapause symptom in C. externa population. These results help to improve the techniques for rearing the species in laboratory conditions.