Wind tunnel behavioural response and field trapping of the blowfly Calliphora vicina

The attraction of the blowfly Calliphora vicina Robineau‐Desvoidy, 1830 (Diptera: Calliphoridae) to single synthetic compounds, blends and authentic odours was investigated in a wind tunnel. A total of 1850 C. vicina (1750 females and 100 males) were tested. A comparison of male and female responses showed significant differences in attraction between the sexes. Females were more attracted than males to liver odour. The attraction of females lay in the ranges of 0–22% for single compounds, 26–64% for synthetic blends and 58–88% for authentic odours. Dimethyl trisulphide was the most attractive single compound. Significant improvement in attraction was achieved with blends and a three‐component lure, consisting of dimethyl trisulphide, mercaptoethanol and o‐cresol, was found to be the best solution for field trapping of C. vicina. Authentic odours from dead fish and mice were significantly more attractive than liver and the three‐component blend, and the blend and liver were similarly effective as attractants. Field tests support the results of the wind tunnel study and a high number of C. vicina were caught in funnel traps. Overall, 99.1% of the specimens caught were females.     

Analysis of the Courtship Behavior of the Navel Orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), with a Commentary on Methods for the Analysis of Sequences of Behavioral Transitions

The courtship behavior of the navel orangeworm, Amyelois transitella, was examined in a wind tunnel. Sixty nine courtship sequences were analyzed and successful sequences divided into two categories: rapid courtship sequences, which involved few breaks in contact, short or no periods of male/female chasing and lasted <10 s between initial contact and mating; and prolonged courtship sequences, which involved many breaks in contact, extended periods of male/female chasing and lasted >10 s. Fifty six (81%) courtships were successful (50.7% rapid courtship and 30.4% prolonged courtship); the remaining 13 (18.8%) sequences were failed courtships. Of failed courtships, 9 (13.0%) were due to males losing contact with females during courtship chases and 4 (5.8%) due to females flying away immediately after male contact. Of all courtship sequences involving a break in contact during a chase, 38.5% resulted in an unsuccessful mating attempt. These findings contrast with previous studies of the courtship behavior of the navel orangeworm, potentially indicating that the type of bioassay used to study courtship may have a large effect on the behavioral sequences displayed. We evaluate several diagnostic techniques for the analysis of sequences of behavioral transitions.     

Geographic variation in fruit volatiles emitted by the hawthorn Crataegus mollis and its consequences for host race formation in the apple maggot fly,Rhagoletis pomonella

The shift of the apple (AP) maggot fly, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), from its ancestral host downy hawthorn, Crataegus mollis (DH) (Torr. & A. Gray) Scheele, to introduced domesticated AP, Malus domestica Borkh. (both Rosaceae), is a model for ecological divergence and incipient sympatric speciation with gene flow. However, a portion of the variation contributing to the sympatric host shift from DH to AP appears to have a different biogeographic history, pre‐dating the shift. One potential source of standing variation may trace to a number of different native hawthorn species infested by R. pomonella in the southern USA, where the AP‐attacking race is absent. Herein, we investigate this possibility for the southern red hawthorn (SR) endemic to Texas, Crataegus mollis var. texana (Buckl.), which has been described as a member of the Molles series that includes the more northern distributed DH. We report results from chemical analyses of host fruit volatiles, fly behavioural responses to synthetic fruit blends, and microsatellite surveys of fly populations, implying that R. pomonella infesting SR may behaviourally and genetically represent a native host race differing from the DH‐infesting fly. No fly reared from SR responded to AP fruit volatiles in flight tunnel assays. However, coupled gas chromatographic‐electroantennographic detection (GC‐EAD) profiles for SR fruit contain all five of the component esters that comprise the standard AP volatile blend inducing behavioural orientation for AP‐infesting flies, compounds that appear to be largely missing from volatile profiles for DH fruit. Thus, SR‐infesting flies do not represent a source for a preassembled AP‐accepting phenotype. However, they may help explain why the ancestral DH race that shifted to AP in the northeastern USA had the ability to recognize AP fruit esters, potentially enabling the shift to AP. Our results highlight how categorizing speciation into different geographic modes may not adequately describe the evolutionary origins of important genetic variation fuelling adaptive radiation and the genesis of new biodiversity.     

BEHAVIORAL EVIDENCE FOR FRUIT ODOR DISCRIMINATION AND SYMPATRIC HOST RACES OF RHAGOLETIS POMONELLA FLIES IN THE WESTERN UNITED STATES

The recent shift of Rhagoletis pomonella (Diptera: Tephritidae) from its native host downy hawthorn, Crataegus mollis, to introduced domesticated apple, Malus domestica, in the eastern United States is a model for sympatric host race formation. However, the fly is also present in the western United States, where it may have been introduced via infested apples within the last 60 years. In addition to apple, R. pomonella also infests two hawthorns in the West, one the native black hawthorn, C. douglasii, and the other the introduced English ornamental hawthorn, C. monogyna. Here, we test for behavioral evidence of host races in the western United States. through flight tunnel assays of western R. pomonella flies to host fruit volatile blends. We report that western apple, black hawthorn, and ornamental hawthorn flies showed significantly increased levels of upwind‐directed flight to their respective natal compared to nonnatal fruit volatile blends, consistent with host race status. We discuss the implications of the behavioral results for the origin(s) of western R. pomonella, including the possibility that western apple flies were not introduced, but may represent a recent shift from local hawthorn fly populations.     

Cowpea weevil flights to a point source of female sex pheromone: analyses of flight tracks at three wind speeds

Abstract.  Two-day-old male cowpea weevils, Callosobruchus maculatus, fly upwind to a point source of female sex pheromone at three wind speeds. All beetles initiating flight along the pheromone plume make contact with the pheromone source. Analysis of digitized flight tracks indicates that C. maculatus males respond similarly to moths tested at several wind speeds. Beetles' mean net upwind speeds and speeds along their track are similar ( P  > 0.05) across wind speeds, whereas airspeeds increase ( P <  0.01) with increasing wind speed. Beetles adjust their course angles to fly more directly upwind in higher wind speeds, whereas track angles are almost identical at each wind speed. The zigzag flight paths are generally narrow compared with most moth flight tracks and interturn distances are similar ( P  > 0.05) at the wind speeds employed. The frequency of these counterturns across the wind line is almost constant regardless of wind speed, and there is little variation between individuals. The upwind flight tracks are more directly upwind than those typically seen for male moths flying upwind toward sex pheromone sources. Male moths typically produce a bimodal distribution of track angles to the left and right of the windline, whereas C. maculatus males' track angles are centred about 0°. Preliminary examination of two other beetle species indicates that they fly upwind in a similar fashion.     

Transversal dose profile reconstruction for clinical proton beams: A detectors inter-comparison

PurposeThe main purpose of this work is the inter-comparison between different devices devoted to the transversal dose profile recostruction for daily QA tests in proton therapy.MethodsThe results obtained with the EBT3 radiochromic films, used as a reference, and other common quality control devices, have been compared with those obtained with a beam profiling system developed at the “Laboratori Nazionali del Sud” of Italian Institute for Nuclear Physics (INFN-LNS, Catania, Italy). It consists of a plastic scintillator screen (thickness 1 mm), mounted perpendicularly to the beam axis and coupled with a highly sensitive CCD detector in a light-tight box.Results and conclusionThe tests, carried out both at the INFN-LNS and Trento Proton Therapy Center facilities, show, in general, a good agreement between the different detectors. The beam profiling system, in particular, appears to be a promising quality control device for 2-D relative dosimetry, because of its linear response in a dose rate range useful for proton therapy treatments, its high spatial resolution and its short acquisition and processing time.     

To what extent can the tiny parasitoid wasps,Eretmocerus mundus,fly upwind?

Body miniaturization in insects is predicted to result in decreased flight speed and therefore limited ability of these insects to fly upwind. Therefore, tiny insects are often regarded as relying on passive dispersal by winds. We tested this assumption in a wind tunnel by measuring the burst speed of Eretmocerus mundus (Mercet), a beneficial parasitoid wasp with body length <1 mm. Insects were filmed flying upwind towards a UV light source in a range of wind speed 0–0.5 m/s. The Insects flew towards the UV light in the absence and presence of wind but increased their flight speed in the presence of wind. They also changed flight direction to be directly upwind and maintained this body orientation even while drifted backwards relative to the ground by stronger winds. Field measurements showed that the average flight speed observed in the wind tunnel (0.3 m/s) is sufficient to allow flying between plants even when the wind speed above the vegetation was 3–5 folds higher. A simulation of the ability of the insects to control their flight trajectory towards a visual target (sticky traps) in winds show that the insects can manipulate their progress relative to the ground even when the wind speed exceeds their flight speed. The main factors determining the ability of the insects to reach the trap were trap diameter and the difference between insect flight speed and wind speed. The simulation also predicts the direction of arrival to the sticky target showing that many of the insects reach the target from the leeward side (i.e. by flight upwind). In light of these results, the notion that miniature insects passively disperse by winds is misleading because it disregards the ability of the insects to control their drift relative to the ground in winds that are faster than their flight speed.     

Synergism of pheromone and host‐plant volatile blends in the attraction of Grapholita molesta males

Control of Grapholita molesta (Busck) (Lepidoptera: Tortricidae), a major pest of stone and pome fruits, is successfully achieved by mating disruption. Under these conditions, tools other than conventional pheromone dispensers are needed for flight monitoring. The objective of the present work was to determine whether plant volatiles synergize male G. molesta attraction to a suboptimal dose of synthetic sex pheromone. The plant blend (referred to as 5VB), a mixture of three green leaf volatiles [(Z)‐3‐hexenyl acetate, (Z)‐3‐hexenol, and (E)‐2‐hexenal] and two aromatics [benzaldehyde (BZA) and benzonitrile (BZN)], was added to the suboptimal pheromone dose (2 ng on filter paper) in log steps (up to 10 000× the pheromone dose) to test synergism of pheromone and plant blends. In addition, the effect of individual plant volatiles on male responses was investigated by adding to the suboptimal pheromone dose each of the four‐compound plant‐volatile blends, resulting from eliminating one volatile from the 5VB at a time, or each plant volatile alone. Flight behaviour and the time to reach the source were recorded. The 5VB alone was not attractive to G. molesta males, but at a ratio of 1:1 000 (Ph:5VB) or higher, the attractiveness of the suboptimal pheromone dose increased, to a level similar to that of the optimal pheromone dose (10 ng). All tested plant volatiles, except BZA, synergized the response to the pheromone when added individually, but only (Z)‐3‐hexenol and BZN did so to a level not significantly different from the Ph:5VB blend. Aromatics had a stronger effect than green leaf volatiles (GLVs), because their removal, but not the removal of GLVs, decreased landing responses. The addition of the 5VB decreased significantly the time males needed to reach the odour source. The observed enhanced male attraction to mixtures of pheromone and plant volatiles will facilitate the development of lures for G. molesta adult flight monitoring.     

The use of temperature gradient tunnels for studying the combined effect of CO2, temperature and water availability in N2 fixing alfalfa plants

Atmospheric CO₂ concentration and temperature are increasing as a consequence of human activity. Periods of low water availability are expected to increase in Mediterranean ecosystems. Temperature gradient tunnels were used to provide near to ambient conditions and conditions simulating predicted increases in CO₂ and temperature for an alfalfa crop. The performance, construction, and running costs of the tunnels are reported and discussed. Two levels of water supply were included in the treatments. Plants were grown in large, 13 L pots, keeping a fixed soil volumetric water content and with nodule fixation as the only nitrogen source for the plant. Regardless of water regime, the effect of elevated CO₂ on plant growth was temperature dependent. Dry matter was enhanced when elevated CO₂ and temperature were combined. Plant yield improvement was partly a result of increased photosynthetic rates. There were no effects on plant N concentration. Decreased specific nodule activity might suggest that lack of differences in plant N were a consequence of reduced nodule enzyme activity.     

Scoliopteryx libatrix (L.) (Lep., Noctuidae) male reaction to the synthetic main sex pheromone component and its isomers – wind tunnel and field investigations

Abstract: The four stereoisomers of 6,13-methylheneicosene were tested with Scoliopteryx libatrix (L.) males in a wind tunnel. The most active isomer was (Z6,S13)-methylheneicosene which had been identified as the main sex pheromone component of the species. Some medium activity was found for (Z6,R13)- and (E6,S13)-, while the (E6,R13)-stereoisomer showed the lowest activity. These results were confirmed in field tests with sticky traps. Monitoring of S. libatrix at two sites showed that the flight of the insects started at the end of March to the beginning of April and lasted till August to the beginning of September. It was concluded that the males of the second generation were not attracted by the pheromone.