The western flower thrips Frankliniella occidentalis (Thysanoptera: Thripidae) is a major insect pest on a wide range of crops throughout the world. There are several unexplained aspects of the mating behaviour, particularly in relation to male-male competition and mate choice. The objectives of the study were to test whether males can detect the mating status of females and whether males avoid mating with previously mated females. Experiments involved either ‘experienced’ adults taken from a laboratory culture, which had been exposed to high densities of thrips, or virgin adults reared individually. Experienced males mated readily with virgin females, but avoided mating with experienced females. Virgin males showed much less discrimination between females. Avoidance of mating with experienced females is likely to be widespread because it occurred in populations from both the United Kingdom and Kenya. Experienced males also mated with dead virgin females, but avoided mating with dead experienced females, which ruled out the possibility that behavioural differences between the females were responsible. To test whether males could detect whether or not females had mated, virgin females of the same age from the same cohort were either mated once or not mated. Experienced males mated with the dead females that were virgin and avoided mating with the dead females that differed only in that they had mated once shortly before. This showed that males recognise whether or not a female has mated and avoid mating with previously mated females. This avoidance by males suggests that mated females are not usually subjected to high levels of male harassment. The most likely explanation of the avoidance is that males produce an antiaphrodisiac pheromone that is applied to females during mating.

The insecticidal properties of Hoslundia opposita Vahl (Lamiaceae) leaves' essential oil (EO) against Tribolium castaneum were investigated using contact toxicity and repellency bioassays. Mortality progressed with exposure period and ranged from 61.13% observed at 24 h after treatment (HAT) to 88.86% at 168 HAT. The LT50 (lethal time for 50% of treated adults) of H. opposita EO against T. castaneum was 10.42 h. Application of EO at 20-30 μL/30 cm(2) caused significantly (P < 0.05) higher percentage repellency than what was observed in control, 10 and 15 μL/30 cm(2) at 1 and 3 HAT, with significant repellency at 24 HAT regardless of dosage. Repellency class increased with EO dosage, with class V observed at 30 μL/30 cm(2), regardless of exposure duration. The RD50 (repellency dose for 50% of treated adults) of 15.88 and 13.37 μL/30 cm(2) for 1 and 2 HAT, respectively, was significantly higher than 0.09 μL/30 cm(2) at 24 HAT.

The natural co-occurrence of aflatoxins (AFs), ochratoxin A (OTA) and citrinin (CIT) in melon seed samples obtained from retailers and households in Ireland and the United Kingdom (UK) was evaluated. AFs and OTA were determined by HPLC with fluorescence detection while CIT was analysed by HPLC-MS/MS. AFB1 was detected in all (100%) samples (mean = 9.7 μg kg(-1); range = 0.2-66.5 μg kg(-1)). Mean total AFs was 12.0 μg kg(-1) (range = 0.3-82 μg kg(-1)). Commercially retailed samples showed a significantly higher AFB1 contamination (p < 0.05) than the household samples. OTA occurred in 3 (13.6%) samples, while 4 (18.2%) were contaminated with CIT at very low levels. In this study, 68% of the melon seed samples were contaminated above the 2 μg kg(-1) EU limit for AFB1 in oilseeds. These results highlight the need for the development of strategies to reduce AF contamination in "egusi" for human consumption.

Many species of thrips (Thysanoptera) in the family Thripidae form mating aggregations, but the adaptive significance of these aggregations and the extent of male and female mate choice is poorly understood. We studied the mating behaviour of the bean flower thrips Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), which forms male aggregations and occurs across sub-Saharan Africa. We tested whether males choose mates by female age or mating status. No-choice mating bioassays with one male and one female were used to simulate the way males usually encounter only one female at a time in aggregations in the field. Virgin females violently resisted mating attempts by males, but we found no compelling evidence to establish whether this was indiscriminate or was screening suitable males. Younger males (1–2 days old) did not discriminate females by age (1–2 or 7–10 days old), but older males (7–10 days old) avoided mating with older females. Any male choice by female mating status (virgin or mated) was weak or absent. The mating behaviour of M. sjostedti shows broad similarities with that of other thrips species that form aggregations, but also shows some distinct and novel differences, which can help our understanding of the adaptive significance of aggregations.