Predicted changes in the synchrony of larval emergence and budburst under climatic warming

Summary The impact of climatic warming on the synchrony of insect and plant phenologies was modelled in the case of winter moth (Operophtera brumata) and Sitka spruce (Picea sitchensis) in the Scottish uplands. The emergence of winter moth larvae was predicted with a thermal time requirement model and the budburst of Sitka spruce was predicted from a previously published model (Cannell and Smith 1983) based on winter chilling and thermal time. The date of emergence of winter moth larvae was predicted to occur earlier under climatic warming but the date of budburst of Sitka spruce was not greatly changed, resulting in decreased synchrony between larval emergence and budburst. The general question of how a change of climate might affect phenological synchrony and insect abundance is discussed.     

Elevated CO2 and herbivory influence trait integration in Arabidopsis thaliana

We lack information on how elevated CO₂, and its interaction with other factors like herbivory, affect levels and patterns of trait integration in plants. We experimentally tested the hypothesis that elevated CO₂ disrupts and restructures functional associations among plant traits, in the selfing annual, Arabidopsis thaliana. We tested for these effects both in the presence and absence of herbivory by larvae of the diamondback moth, Plutella xylostella. Elevated CO₂, both alone and combined with moth herbivory, modified integrated trait responses. In addition, integration under different environments was genotype‐specific. These results imply that global changes in CO₂ are likely to cause divergent evolutionary outcomes among populations of plants that differ in the initial structure of their quantitative genetic variation.     

Influence of ambient and thoracic temperatures upon sexual behaviour of the gypsy moth, Lymantria dispar

ABSTRACT. In an ambient temperature ( T _a) range of 18–28°C, thoracic temperatures ( T _th) of individual male Lymantria dispar (L.), caught at flight in the field, ranged from 21 to 36.5°C, with a correlation coefficient of 0.63 between T _th and ambient temperature ( T _a). Ambient temperature (and insolation) altered the insect's body temperature and the probabilities, latencies, and durations of preflight responses to pheromone. In a wind tunnel at 16 and 20°C, quiescent males exposed to pheromone raised their T _th by sustained wing fanning from 17 and 21°C, respectively, to c. 24°C before takeoff. At 24 and 28°C ambient, T _th rose by takeoff to 28 and 31°C, respectively. The latencies of male wing fanning in response to pheromone decreased from 1.44 min at 16°C ambient, to 0.58 min at 20°C, to 0.26 min at 24°C, and to 0.16min at 28°C. The components of behaviour (antennal twitch, body jerk, step and wing tremor) that occurred between quiescence and wing fanning were more frequent at ambients of 16 and 20°C than at 24 and 28°C.     

Pupation site preference and body orientation of the potato tuber moth, Phthorimaea operculella

ABSTRACT. Pupation site preference and body orientation of potato tuber moth larvae, Phthorimaea operculella Zeller (Geleehiidae), were examined in the laboratory. The larvae preferred a dry, enclosed, dark place as their pupation site. Dryness was the strongest of the three categories of stimulus; the second was stimuli evoking thigmotaxis; the third was darkness. Having selected a pupation site, a larva oriented its head to the open side of the site. If two or more openings were present, final orientation was influenced by light and gravity. These preferences and orientation habits enhance pupal protection, and the ultimate successful exit of the adult pupation crevices.     

Daily rhythm in myogenic contractions of vas deferens associated with sperm release cycle in a moth

In the gypsy moth, Lymantria dispar, release of sperm bundles from the testis into the upper vas deferens (UVD) and subsequent transfer of sperm bundles into the seminal vesicles (SV) occurs in a daily rhythm. The UVD undergoes different types of contractions despite the fact that its musculature appears to receive no innervation. Patterns of the UVD movements were recorded throughout the daily sperm release and transfer cycle. In males kept in light-dark cycles, transfer of sperm from the UVD to the SV was accompanied by a characteristic pattern of UVD contractions of high frequency and amplitude. In males kept in constant light, which fail to transfer sperm, this contraction pattern was absent. It is concluded that the vas deferens muscles undergo daily changes in contraction pattern in phase with the light-dark cycle. The increased muscular contractions appear to be a causal factor in the gated sperm transfer from the UVD to the SV.Abbreviations LD light-dark - LL constant light - SV seminal vesicle - UVD upper vas deferens     

Interacting effects of photophase and scotophase on the diapause response of the Indian meal moth, Plodia interpunctella

The diapause-programming response to photoperiod in Plodia interpunctella was analyzed by exposing larvae to various 24-h and non-24-h regimes of light and darkness. The response to 24-h regimes indicated three photoperiodic parameters—a critical scotophase, a minimal photophase, and a minimal scotophase for a full expression of the response. The critical response was based on dark-time measurement, because disruption of the scotophase abolished the response and the diapause incidence varied as a function of scotophase in non-24-h regimes. The critical scotophase varied with the duration of the preceding photophase. Prevention of diapause by single or double-night interruptions of long scotophases could be explained by resetting of the dark-time measurement. The effect of a light pulse was modified by the quantitative interaction of light and dark reactions. The sensitivity to resetting by a light pulse seemed to be decreased in the early scotophase with an increasing duration of the preceding light period. Therefore, the significance of light in the photoperiodic response was something more than delimiting scotophase for the time measurement.     

Predicting the impacts of climate change on the biological control of Plutella xylostella by Diadegma semiclausum

1. The parasitoid Diadegma semiclausum Hellén (Hymenoptera: Ichneumonidae) has been widely adopted as a biological control agent for Plutella xylostella L. (Lepidoptera: Plutellidae) over the last 80 years. Earlier studies have found differential responses to temperature between the host and its parasitoid and demonstrated the multiple ways in which the parasitoid is more susceptible to elevated temperatures.
2. Using data from experimental studies, the modelling package CLIMEX was used to investigate the suitability of current climates for the host and its parasitoid and the effects on their potential global geographical distributions. The study was then extended to investigate possible changes to these distributions that might result under different climate change scenarios by 2080. The models predict that the global distributions of both the host and parasitoid will be reduced. These changes will not be proportionate and many areas in tropical, sub-tropical, and temperate regions that are currently suitable for D. semiclausum are predicted to become unsuitable for the parasitoid, whereas retaining suitability for P. xylostella. The seasonal dynamics of both the host and parasitoid are also predicted to be significantly reshaped under climate change.
3. Analysis of associations between annual P. xylostella outbreaks and weather conditions in three provinces in China with field data collected between 1995 and 2017 indicated significant effects of temperature on P. xylostella outbreaks at the beginning of the peak season in warmer provinces where P. xylostella can overwinter; such associations were not found in the colder provinces where it is unable to survive harsh winters.

     

Effect of abscisic acid and proline on <Emphasis Type="Italic">in vitro</Emphasis> flowering in <Emphasis Type="Italic">Vigna aconitifolia</Emphasis>

An experiment was taken up to find out possibilities of manipulating the in vitro flowering in moth bean. Abscisic acid (ABA) and proline both alone and in combination influenced days to flower induction, number of flowers per plant, number of pods per plant and seeds per pod. Frequency of flowering plants approached 100 % at 1 and 3 μM ABA and 800 μM proline. The range of flowering period (3 to 23.6 d) has also been influenced by various treatments.