Fig 1.
Experimental area for seasonal egg laying dynamics and first annual egg hatching monitoring of Aedes albopictus in Mediterranean France.
The area monitored by ovitraps from summer solstice 2010 to summer solstice 2012 was computed as the surface of the smallest polygon including all traps with a buffer distance of 50 m (black area). This area was safe from outdoor insecticide spraying for vector control (circles). Ten infested places localized around the ovitraps network were inspected daily in March 2011 and 2012 to detect the first larvae of the year (triangles).
Fig 2.
Protocol for the determination of egg diapause incidence in Aedes albopictus.
The critical photoperiod (CPP) of the population is determined by an experiment including all steps in this order: A, B, C, D, E, B, C and F (black arrows). The survey of diapause incidence in the field follows steps A, B, C and F (green arrows).
Fig 3.
Photoperiodic analyses of egg diapause induction and initiation in Aedes albopictus.
X axis represents the mean daylight duration during the egg laying week in the field in 2010 (green diamonds, n = 10) and 2011 (red dots, n = 36). Photoperiod inducing diapause was studied at fixed day length in laboratory (blue squares, n = 15). Sigmoid curves modeled for egg diapause incidences are in bold solid line (laboratory) or solid dashed lines (field). Smooth dotted lines represent the 95% confidence intervals. The sigmoid response curves ignore the field data points of decreasing diapause incidence for day length ≤ 11.5 hours, as these outliers are probably the result of a selection trend. The horizontal dot line (light grey) marks 50% of diapause incidence. The difference between blue curve (laboratory data) and green and red curves (field data) highlights the delay between maternal diapause induction and diapause preparation in offspring.
Fig 4.
Seasonal profiles of oviposition activity and diapause timing of Aedes albopictus population (A,B) from summer solstice 2010 to summer solstice 2012 under the Mediterranean climatic conditions (C,D) of the city of Cagnes-sur-Mer, France.
Asterisk represents positive samples with less than 100 eggs collected. Arrows show the week of sampling of the first larvae of the year.
Table 1.
Comparison of theoretical and field observed development time of Aedes albopictus stages using a day-degree model.
The thermal threshold is equal to 11°C.
Fig 5.
Schematic depiction of the seasonal activity and diapause process of Aedes albopictus population in the Mediterranean city of Cagnes-sur-Mer, France.
Horizontal lines represent the mean durations of diapause syndrome and of the long generation of A. albopictus. Vertical lines delineate the moment when diapause is induced (in red) or initiated (in dark) in 50% of eggs, and the start of diapause termination (in green).