Calling Behavior in the Primitive Longhorned Beetle Prionus californicus Mots.

Many prionine species share morphological and behavioral traits commonly associated with production of volatile pheromones by females. Adults Prionus californicus Mots. are sexually dimorphic, males being smaller and having antennae that are much more strongly serrate than those of females. Females of this species produce a volatile pheromone that attracts males. We conducted studies characterizing calling behavior of P. californicus females. In these studies females typically lowered their heads and raised their abdomens while extending their ovipositors. The extended ovipositor was often flexed and the abdomen rhythmically contracted during these bouts which lasted up to 10 min. In some cases females everted a membranous, cylindrical sac from the dorsal surface of the ovipositor which was retracted before the ovipositor was withdrawn. This eversible sac has not reported for a cerambycid species, and is likely to be involved in production and/or release of pheromone.     

大螟成虫性信息素生物合成和释放及求偶和交配行为的昼夜节律

【目的】探索大螟Sesamia inferens性信息素顺11-十六碳烯乙酸酯(Z11-16∶Ac)和顺11-十六碳烯醇(Z11-16∶OH)的合成和释放及求偶和交配行为的昼夜节律,及其与田间性信息素诱捕的关系。【方法】通过溶剂浸提和固相微萃取(solid phase microextraction, SPME)分析大螟雌蛾性信息素Z11-16∶Ac和Z11--16∶OH的滴度,结合行为观测和多地田间实时性信息素诱捕数据,调查大螟性信息素的生物合成、释放及求偶和交配行为的昼夜节律。【结果】大螟雌蛾腺体内性信息素Z11-16∶Ac和Z11-16∶OH含量可检测到的时间始于暗期前1 h,暗期后4 h快速增加,暗期8 h为第1次高峰,但光期1h又一次高峰,光期5 h还可以被显著检测到。分泌至腺体外的性信息素化合物可检测到的时间始于暗期后6 h,高峰期在暗期后10 h,光期后1 h性信息素Z11-16∶Ac滴度达到96.9±20.9 ng/雌。采用溶剂浸提法获得的Z11-16∶Ac和Z11-16∶OH的比例在暗期平均为2.8±1.9,在光期平均为2.5±0.9,统计上二者没有显著差异,而SPME法获得的Z11-16∶Ac和Z11-16∶OH的比例在暗期平均为8.5±1.2,在光期平均为5.7±0.6,统计上二者差异显著。产卵器伸出时间发生在暗期6-8 h,产卵器伸出持续时间平均为80.8±4.4 min。大螟的交配发生在暗期4-10 h,交配持续时间平均为83.4±5.0 min。广东、四川、浙江、江苏四省性诱自动计数的田间每日每小时实时计数数据显示,越冬代诱蛾比较集中,之后的世代则比较分散,田间雄蛾的性诱昼夜节律受地理环境、季节和世代等因子的影响。【结论】本研究发现大螟交配和性信息素释放的昼夜节律在时间上不一致,交配时间在暗期较早时段。雌蛾性信息素有效的释放时间范围比雄蛾对性信息素反应的要小。产卵器伸展与雌蛾性信息素化合物的释放速率加快和扩散 范围有关。     

Toward the Identification of the Sex Pheromone of Diatraea indigenella Dyar & Heinrich (Lepidoptera: Crambidae): Calling Behavior and Chemical Structure of a Major Component

Behavioral patterns and pheromone titer in females of the steam borer Diatraea indigenella Dyar & Heinrich were assessed for 7 days during scotophase under a 13:11 L:D photoperiod. Calling was observed from the first scotophase for most of the females. The highest percentage of calling females was recorded 6 h after the onset of scotophase. Calling bouts and length of calling were affected by age, decreasing dramatically after the sixth scotophase. By coupling chemical and electrophysiological techniques (GC–EAD, GC–MS) and olfactometer bioassays (Z,E)-9,11-hexadecadienal was identified as the main sex pheromonal component in the extracts of female glands. The concentration varied from 2.53 to 13.7 ng gland^?1 with a peak at the 6th hour of scotophase. In addition, two unidentified secondary active components were detected at very low concentrations. Behavioral assays showed that 86% of the male moths were more attracted to the gland extracts than to hexane (control), and 77% of the male moths were more attracted to the gland extract than to the synthetic major component (Z,E)-9,11-hexadecadienal. However, 68% of males preferred the synthetic major component over hexane. The identification of the major sex pheromonal component represents an important step toward the complete elucidation of the composition of the sex pheromone of D. indigenella in order to develop monitoring tools.     

Pupal Period Affects Calling Behavior of the Wheat Moth, Pseudaletia sequax (Lepidoptera: Noctuidae)

The effects of pupal period and age on calling behavior of virgin females of Pseudaletia sequax were determined. Calling behavior of groups of females of similar age of pupation was observed every 10 min for six calling days. Females were considered calling when they assumed a characteristic position: wings and abdomen elevated, displaying the ovipositor and presumably releasing pheromone. Calling behavior was discontinuous. Females with a shorter pupal period took more time to start calling than females with a longer pupal period and called for a longer period. On the first day of calling, females took more time to initiate calling, on average during the seventh hour of the scotophase, whereas on the second day of calling, most females initiated calling during the fifth hour of the scotophase. On subsequent days of calling, the average time to initiate calling changed to the fourth hour of the scotophase. The mean time of calling per day decreased significantly with the number of days since first calling, and the mean number of calling bouts increased with days since first calling.     

Age-dependent pattern of calling behavior in <Emphasis Type="Italic">Atheloca subrufella</Emphasis> (Hulst) (Lepidoptera: Phycitidae)

Changes in the signaling effort of virgin females are known to occur until their first mating. Young females tend to increase the calling effort (number and time duration of bouts) as they age. In this context, the calling behavior of virgin females of Atheloca subrufella, an important pest of coconut palms (Cocos nucifera), was studied under laboratory conditions. Thirty four virgin females were observed during 16 scotophases (25 ± 2 °C, 75 ± 5 % RH and 10 h scotophase), until they stopped calling in the following photophase. The calling position, pattern and frequency were evaluated. Females of A. subrufella showed only one calling position, and calling peaked between the second and fifth scotophases. Most females did not start calling immediately after emergence. Neither the individual duration of calling nor the number of calling bouts changed over time. However, the time that calling started was earlier in older females, probably to avoid competition with younger females and increase the probability of mating. These data support the hypothesis that there is an age-dependent pattern of pheromone emission in virgin females of A. subrufella.     

Temporal distribution of PBAN‐like immunoreactivity in the hemolymph of Mamestra brassicae females in relation to sex pheromone production and calling behavior

A direct enzyme‐linked immunosorbent assay has been developed and applied to the analysis of PBAN immunoreactivity in female hemolymph of the cabbage armyworm, Mamestra brassicae. PBAN‐IR determinations have been carried out with third scotophase insects at different times of the photoperiod. The rhythm of calling and the pattern of pheromone production by third scotophase females at different times of the photoperiod have also been determined. PBAN‐IR and calling are well correlated. However, whereas pheromone titers decrease, both PBAN‐IR levels and percentage of calling females remain high in the last hours of the scotophase. These results are discussed in the context of the regulation of sex pheromone biosynthesis in M. brassicae. Arch. Insect Biochem. Physiol. 40:80–87, 1999. © 1999 Wiley‐Liss, Inc.     

Environmental regulation of female calling and male pheromone response periodicities in the codling moth (Laspeyresia pomonella)

Codling moth female calling and male pheromone responsiveness under the defined conditions of 23°C and light:dark (LD) 16:8 occurred primarily during scotophase. Under either continuous photophase or scotophase females called with periodicities very similar to their periodicity under the LD cycle, indicating that the rhythmicity is circadian. Male response rhythmicity was maintained under continuous photophase. A decrease in the temperature from 23° to 16°C resulted in a reduction in the proportion calling when the decrease in temperature occurred during scotophase and a shift of maximal calling into photophase when the decrease in temperature occurred 3 hr prior to the initiation of scotophase. Decreases of temperature from 23° to 16°C and of light intensity did not produce similar shifts in the periodicity of male upwind orientation. Of 6 pheromone dosages from 10^?5 to 10² μg, 10^?1 and 10⁰ μg elicited the most male upwind orientation.     

Sex pheromone titre in the glands of Spodoptera litura females: circadian rhythm and the effects of age and mating

The present study investigates the effects of age and mating status on the circadian variations of gland sex pheromone titre in female Spodoptera litura Fabricius. Similar to other nocturnal moths, S. litura females exhibit circadian variations of gland sex pheromone contents, with higher levels during scotophase and lower levels during photophase. The sex pheromone titre in the glands peaks during the first scotophase after eclosion and sharply declines afterwards. Higher pheromone contents during scotophase may facilitate female reproductive activities, and the negative relationship between pheromone titre and female calling is likely the result of pheromone release during female calling. Interestingly, the present study demonstrates that mated S. litura females have significantly higher sex pheromone titre in their pheromone glands (PGs) than virgin females. This finding contrasts with all previous studies of other insect species, in which mating generally reduces the sex pheromone titre in female PGs. In S. litura, mating and male accessory gland fluids can suppress female calling behaviours and re‐matings. These results suggest that the suppression of female calling behaviours by mating and male accessory gland fluids may significantly reduce the release of sex pheromones and thus result in higher sex pheromone titre in the PGs of mated females.     

DIEL RHYTHMS OF CALLING BEHAVIOR AND SEX PHEROMONE PRODUCTION OF BEET ARMYWORM,SPODOPTERA EXIGUA (LEPIDOPTERA:NOCTUIDAE)*

Abstract Beet armyworm (BAW), Spodoptera exigua, is becoming one of more and more serious pests in China in recent years. As a part of research program of sex pheromone and its application of BAW in China, the hourly and daily variation of calling behavior and pheromone production of BAW females were investigated. Both calling behavior and titers of 4 sex pheromone components showed distinct diel rhythms, and the two peak periods were synchronous. In comparison, the calling activity lasted shorter period of time with a longer peak time, whereas the production of the sex pheromone lasted throughout the whole scotophase and part of the photophase with a very short peak time. The calling behavior began at the middle scotophase, reached the maximum at the middle‐later scotophase, and continued the maximal calling activity until the end of the scotophase. When the light was on, the calling percentage reduced sharply, and all females stopped calling 1 hour later. The variation patterns of the 4 pheromone components in the glands of the 3 day old moths were similar from one to another. From 0.5 h before to 4.5 h into scotophase, the titers increased slightly, but at 6.5 h they showed a significant increase up to the peak values of the scotophase. Soon at 8.5 h into the scotophase, they decreased significantly and thereafter gradually to undetectable level at 4.5 h into the next photophase. The daily change experiment showed that BAW females began calling at 0 scotophase, became fully active in calling at 3rd scotophase, and maintained the calling activity to 7th scotophase. There was no significant difference in pheromone titers among different day‐old moths.     

Preference for high concentrations of plant pyrrolizidine alkaloids in the specialist arctiid moth Utetheisa ornatrix depends on previous experience

Secondary metabolites are one the most pervasive defensive mechanisms in plants. Many specialist herbivores have evolved adaptations to overcome these defensive compounds. Some herbivores can even take advantage of these compounds by sequestering them for protection and/or mate attraction. One of the most studied specialist insects that sequesters secondary metabolites is the arctiid moth Utetheisa ornatrix. This species sequesters pyrrolizidine alkaloids (PAs) from its host plant, the legume Crotalaria spp. The sequestered PAs are used as a predator repellent and as a mating pheromone. We used this species to test larval preference for different concentrations of PAs. We purified PAs from plant material and added them at different concentrations to an artificial diet. Larvae of U. ornatrix previously feeding on low and high PA concentration artificial diets were allowed to choose between two new artificial diets with different PA concentrations. The amount of PAs sequestered and larval preference were dependent on their previous exposure to low or high PA content in the diet. Larvae that were pretreated with a low PA diet significantly consumed more diet with the high PA concentration, while larvae that were pretreated with a high PA diet showed no discrimination between future feeding of different PA concentration diets. We discuss our results using mechanistic and evolutionary approaches. Finally, we discuss how these results have important implications on the evolution of plant herbivore interactions and how specialist herbivores may decrease the levels of chemical defenses on plant populations.     

Mating behaviour of the corn stalk borerSesamia nnonagrioides

The mating behaviour of the corn stalk borerSesamia nonagrioides (Lef.) [Lepidoptera:Noctuidae] was studied under laboratory conditions at 25 ± 1 °C, 65 ± 5% r.h. and 16:8 (L:D) regime. The females began calling during the first scotophase following emergence, the peak of calling occurred during the second scotophase and thereafter decreased. Maximum calling was observed between the fourth and sixth hour of the scotophase. The calling pattern varied with age. During the first and second scotophase most of the females were calling continuously, while during the third and fourth scotophase periodic calling was observed. The mean onset of calling was advanced and the mean length of calling per day was increased slightly as the female became older. Females held for 72 h in continuous darkness exhibited an endogenous circadian rhythm of calling. Matings began during the first scotophase following emergence and the peak of mating was observed during the second scotophase. Mated females did not remate. Few males mated more than once during the following scotophases.     

Sex pheromone-releasing behaviour in females of the dermestid beetle,Trogoderma glabrum

Adult Trogoderma glabrum females assume stationary postures characterized by abdominal elevation and partial exposure of the ovipositor segments. The postural activity was studied in relation to sex pheromone production and was designated calling, or sex pheromone-releasing behaviour because it was accompanied by an increase in the rate of release of sex pheromone(s). Calling was largely restricted to an 8 hr interval centered toward the middle of a 16 hr photophase. Mating frequency and female pheromone content increased during the same interval. Because females extracted during the calling period yielded at least 10 times more pheromone than extracts prepared at other times, and because pheromone activity released during one calling period was estimated to be at least 10-fold higher than that which could be extracted from whole females several hours prior to the start of calling, heightened production of active pheromone(s) was postulated to occur during calling. Functional significance of the calling posture is discussed in relation to sex pheromone gland location.     

Sublethal effects of chlordimeform on chemical communication and other reproductive behaviors in the female cabbage looper moth (Lepidoptera: Noctuidae)

Insecticides can affect the complex coordination of activities associated with reproduction through their sublethal impact on the nervous system. Our objective was to document the effects of a sublethal dose (1% mortality) of chlordimeform on reproductive events in the female cabbage looper moth, Trichoplusia ni. A significantly higher percentage of females treated with chlordimeform initiated calling at some time during the scotophase. Chlordimeform stimulated pheromone emission early in the scotophase. However, late in the scotophase pheromone emission was significantly lower in chlordimeform-treated females when compared with control females. Overall, a lower amount of pheromone was detected in glands of chlordimeform-treated females. This effect was significant only during the second half of the scotophase. We suggest that chlordimeform stimulates pheromone transport to the gland surface and calling behavior resulting in depletion of pheromone reserves over the course of the scotophase. Chlordimeform also decreased the mating success of males. Oviposition and egg hatch were also affected by chlordimeform. Mated females treated with chlordimeform laid significantly fewer eggs than acetone-treated females. In addition, hatchability of eggs laid by mated female T. ni treated with chlordimeform was significantly lower than for eggs laid by control females.     

The making of a pest: the evolution of a fruit-penetrating ovipositor in Drosophila suzukii and related species

Evolutionary innovation can allow a species access to a new ecological niche, potentially reducing competition with closely related species. While the vast majority of Drosophila flies feed on rotting fruit and other decaying matter, and are harmless to human activity, Drosophila suzukii, which has a morphologically modified ovipositor, is capable of colonizing live fruit that is still in the process of ripening, causing massive agricultural damage. Here, we conducted the first comparative analysis of this species and its close relatives, analysing both ovipositor structure and fruit susceptibility. We found that the ovipositor of the species most closely related to D. suzukii, Drosophila subpulchrella, has a similar number of enlarged, evolutionarily derived bristles, but a notably different overall shape. Like D. suzukii, D. subpulchrella flies are capable of puncturing the skin of raspberries and cherries, but we found no evidence that they could penetrate the thicker skin of two varieties of grapes. More distantly related species, one of which has previously been mistaken for D. suzukii, have blunt ovipositors with small bristles. While they did not penetrate fruit skin in any of the assays, they readily colonized fruit interiors where the skin was broken. Our results suggest that considering evolutionary context may be beneficial to the management of invasive species.     

Mechanisms of premating isolation between Helicoverpa armigera (Hübner) and Helicoverpa assulta (Guenée) (Lepidoptera: Noctuidae)

Helicoverpa armigera and Helicoverpa assulta are sympatric sibling species, and in the laboratory they can interbreed and produce viable offspring. To assess the contributions of temporal barriers and sexual barriers to premating isolation, we investigated both the temporal rhythms of calling behavior and pheromone titers of H. armigera and H. assulta females and the behavioral responses of males to conspecific and heterospecific calling females in a wind tunnel. Both H. armigera and H. assulta females called throughout the scotophase, and there was more calling during the second half of the scotophase than during the first half. Maximal pheromone titer and maximal calling activity in H. armigera synchronously occurred at the sixth hour into the scotophase, whereas, in H. assulta, the maximal pheromone titer occurred 2 h before the peak of calling. Pheromone blend ratios of the two species were opposite and, within each species, changes in the ratio within the scotophase and at different ages were relatively small. Males of both H. armigera and H. assulta responded strongly to their conspecific calling females in the wind tunnel and completed the whole courtship sequence. In contrast, they did not land and had no copulation attempts in response to heterospecific calling females. These results show that the two species do not have obvious temporal differences in calling behavior and pheromone production, and the specificity of sex pheromone blend emitted by females plays a key role in their premating isolation. In addition, we summarized the potential isolation mechanisms of H. armigera and H. assulta.     

The effect of photoperiod on the calling behaviour of virgin females of the true armyworm,Pseudaletia unipuncta (Haw.) (Lepidoptera: Noctuidae)

The effect of photoperiod on the calling behaviour of Pseudaletia unipuncta virgin females was examined under five different photoperiodic regimes at 25°C, 65% r.h. The age at which females called for the first time following emergence varied with photoperiod; generally calling was later under long-scotophase conditions. However under a 6 h scotophase there was also a delay in calling and >63% of the females tested never called. There was a considerable variability in the daily calling patterns between the different photoperiods, and the mean onset time of calling was not constant with either “lights on” or “light off”. There was however a constancy of the mean onset time of calling relative to the mid-point of both the photo- and scotophase at all photoperiods tested, indicating that females could measure the absolute duration of either the photo- or scotophase. Transferring females from one photoperiodic condition to another once calling had been initiated, determined that it was the “lights off” signal that P. unipuncta females used to phase set the clock governing circadian calling behaviour.Females subjected to a decrease of 4 or 6 h in the length of the scotophase following the initiation of calling required several days to adjust to the new photoperiodic regime and a high proportion of females did not call during the night following the transfer. A 4 or 6 h increase in the scotophase did not inhibit calling on the night following the transfer but females still required several days to adjust completely. However, females experiencing a 2 h increase or decrease in the duration of the scotophase were able to maintain normal calling behaviour. The results of these experiments are discussed in relation to the seasonal biology of the true armyworm and the hypothesis that this is a migrant species.     

Calling Behavior and Rhythms of Sex Pheromone Production in the Black Cutworm Moth in China

The hourly and daily variation of calling behavior and sex pheromone production by the female black cutworm moth, Agrotis ypsilon (Rottemberg), were investigated. Both calling behavior and titers of five sex pheromone components showed distinct diel rhythms, and peak periods of calling and pheromone titer were synchronous. Females began to call on the first night after eclosion and called mainly during the second half of the scotophase. The percentage of females calling increased in 1 to 3-d-old females and decreased in 3 to 7-d-old females. Females advanced their calling time with increasing age (1 to 7 d). GC-MS analysis of hexane extracts of pheromone glands revealed that the titers of the five sex pheromone components were very low on the first night after eclosion, but increased sharply and peaked on the third night. Titers decreased greatly with increasing age (3 to 7 d), but from the onset of the scotophase to 4.5 h into scotophase, titers remained invariate. However, from 4.5 to 7 h, pheromone titers, especially that of the primary component Z7-12:Ac, increased sharply and peaked. After the peak, the titers decreased greatly at 8 h, and thereafter decreased gradually to the level before 4.5 h. The quantity of each component almost reached zero after lights-on.     

Rate and diel periodicity of pheromone emission from female gypsy moths, (Lymantria dispar) determined with a glass-adsorption collection system

The rate of pheromone emission from wild and laboratory-reared gypsy moth (Lymantria dispar) (Lepidoptera: Lymantriidae) virgin females was determined with an all-glass aeration apparatus. This device incorporated a bed of 1-mm glass beads to extract entrained pheromone from the air flowing over the protruded gland. The temporal pattern of emission was established by monitoring individual females after eclosion for 24 consecutive 2-hr intervals.At a constant 24°C, both wild and laboratory females exhibited a similar diel periodicity of pheromone emission. The mean release rate increased after onset of photophase, generally attained maximal levels between 1600 and 2200 hr and declined during scotophase. Pheromone was released continuously and the mean daily emission increased with age for both wild and laboratory moths. The mean emission rate over the 48-hr monitoring interval was $\text{15.4 ng}\text{2 hr}$ for wild females vs $\text{14.7 ng}\text{2 hr}$ for laboratory moths. The peak emission from 2-day-old laboratory moths was ca.$\text{28 ng}\text{2 hr}$ compared with the ca.$\text{25 ng}\text{2 hr}$ released by their wild counterparts.The calling periodicity of laboratory females was determined at a constant 24°C and under a natural temperature rhythm. At 24°C, the proportion of females calling exceeded 45% throughout the diel period, whereas under the temperature rhythm, calling was virtually eliminated by temperatures below 15°C, indicating that temperature acts as an exogenous cue to modify the expression of the calling rhythm and thus potentially the periodicity of pheromone emission.     

Nocturnal Calling Behavior in Mantids

Females of Mantis religiosa and Empusa pennata were video taped for several 24 h periods to determine if they showed behaviors associated with pheromone release. In the photophase the abdomen of both species was motionless and rested in continuous contact with the wings. However, at the beginning of the scotophase the females bent the abdomen ventrally so that the space between the abdomen and the wings increased significantly with respect to the daytime posture. Calling behavior (abdominal bending) was maintained throughout the 8 h scotophase and ended abruptly at lights on. Females of M. religiosa did not start calling until they were 30 days of age. Calling disappeared in mated females, but it reappeared two weeks later. Males stayed motionless in response to the odors emitted by other males or by noncalling females, but walked when a calling female was placed in the air flow. These observations suggest that female mantids bend their abdomens at night to release a sex pheromone. The adaptive function of nocturnal sex pheromone release in sexually cannibalistic species that rely strongly on visual cues for mating is discussed.     

Predation on the woodwasp Tremex longicollis Konow (Hymenoptera: Siricidae) and its parasitoid Megarhyssa jezoensis (Matsumura) (Hymenoptera: Ichneumonidae) adults during oviposition

Adults of the woodwasp Tremex longicollis Konow (Hymenoptera: Siricidae) oviposit in the wood of dying Celtis sinensis trees using their ovipositors, and adults of the parasitoid Megarhyssa jezoensis (Matsumura) (Hymenoptera: Ichneumonidae) deposit eggs into the woodwasp larvae that live in the wood, also using their long ovipositors. Many T. longicollis ovipositors, both with and without abdominal segments, and a M. jezoensis ovipositor were found stuck in C. sinensis wood at two parks in Osaka Prefecture, central Japan. Field observations showed that ovipositing woodwasps and parasitoids were attacked by predators during the daytime, and their ovipositors were left behind in the wood. Woodwasps and their parasitoids, which have long ovipositors, may be vulnerable to predation during oviposition.