The potential use of stable isotopes to study mosquito mating was investigated by tracing the fate of labelled semen into spermathecae.[13C]glucose was incorporated in the diet of the malaria mosquito Anopheles arabiensis. Treatments included labelling of either the larval water or adult sugar water, or a combination of both. After mating,`spiked' spermathecae were analysed for isotope ratios using mass spectrometry. Results demonstrated that spermathecae positive for semen could successfully be distinguished from empty ones or controls (i.e. filled with unlabelled semen) using the raw δ13C values. Labelling during larval development and combined labelling of larvae and adults resulted in detectable values. The label persisted in spermathecae for up to 7 days after mating, and unlabelled sugar feeding of males labelled in the larval stage did not result in a detectable turnover of the semen label. There were no detrimental effects of the addition of labelled glucose on larval development and survival, adult size, male longevity and mating performance. We have proved that it is possible to label male mosquitoes and detect the semen label in females after insemination. This method offers great potential to study mating in mosquitoes and other insects and could prove useful in genetic control studies of medical or agricultural pest insects, with male mating success in the field as a critical verifiable indicator for a positive outcome of the intervention.

The purpose of this study was to examine how differences in leaf angle, leaf rolling (LR) and glaucousness (GL) can modify yield components and leaf physiological traits in wheat. A set of 167 lines derived from a cross between two high-yielding bread wheat cultivars differing for these traits was grown under flood irrigation and high evaporative demand in the north-west of Mexico. Area, mass per unit area and chlorophyll content of the flag leaf were assessed. Carbon isotope discrimination (D) and ash content (m a ) were also measured. A significant correlation was found between grain yield (GY) and both D and m a suggesting that, despite well-watered conditions, leaf stomatal conductance was the main yield-limiting factor. Leaf posture and LR did not significantly affect yield, D and m a . Higher grain weight was noted, however, in lines with droopy flag leaves. Erect leaves had higher mass per unit area. GL was associated with a significant increase in GY and grain weight. Glaucous lines also had higher D and m a , suggesting higher transpiration rate and lower transpiration efficiency. The study confirms that D and m a represent promising criteria for GY in wheat and provides evidence that GL can contribute to higher yield, even under irrigated conditions.

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Background: Monitoring of sterile to wild insect ratios in field populations can be useful to follow the progress in genetic control programmes such as the Sterile Insect Technique (SIT). Of the numerous methods for marking insects most are not suitable for use in mass rearing and mass release. Suitable ones include dye marking, genetic marking and chemical marking.

In previous studies it was determined that the stable isotope 13-carbon can be used as a semen label to detect mating events in the malaria mosquito Anopheles arabiensis. In this paper we describe the use of an additional stable isotope, 15-nitrogen (15N), for that same purpose. Both stable isotopes can be analysed simultaneously in a mass spectrometer, offering the possibility to detect both labels in one sample in order to study complex and difficult-to-detect mating events, such as multiple mating. 15N-glycine was added to larval rearing water and the target enrichment was 5 atom% 15N. Males from these trays were mated with unlabelled virgin females, and spiked spermathecae were analysed for isotopic composition after mating using mass spectrometry. Results showed that spermathecae positive for semen could be distinguished from uninseminated or control samples using the raw delta15N per thousand values. The label persisted in spermathecae for up to 5 days after insemination, and males aged 10 days transferred similar amounts of label as males aged 4 days. There were no negative effects of the label on larval survival and male longevity. Enrichment of teneral mosquitoes after emergence was 4.85 +/- 0.10 atom% 15N. A threshold value defined as 3 standard deviations above the mean of virgin (i.e. uninseminated spermathecae) samples was successful in classifying a large proportion of samples correctly (i.e. on average 95%). We conclude that alongside 13C, 15N can be used to detect mating in Anopheles and the suitability of both labels is briefly discussed.