To seek sufficient resources for growth, survival and reproduction, most insect species must tackle host selection problems. The development, survivorship and fecundity of the oriental fruit moth Grapholita molesta (Busck) on apricot Prunus armeniaca L., plum Prunus salicina L., nectarine Prunus persica var. nectarina L. Batsch, peach Prunus persica L., pear Pyrus sorotina Will. and apple Malus domestica Mill. were determined to test host suitability in the laboratory. Larval development rate was faster, and survival rate was higher on plum and nectarine compared with the other fruits. Adult longevity and the duration of oviposition were significantly longer on nectarine. Adult fecundity varied significantly among the tested host plants, with the highest fecundity being observed on apple (135.63 eggs/female), followed by pear (104.90 eggs/female). The intrinsic rate of increase (r m ) was greater on pear and apple (0.1574 and 0.1221 eggs per female per day, respectively). Different abilities to develop and reproduce on various host plants partly explain the seasonal host selection of G. molesta.

Plant colouration is known to be used by some nocturnal flower-visiting insects to foraging among colourful flowers in dim light. However, it remains unknown whether crepuscular species possibly reliably discriminate plant colouration (i.e. colour and/or brightness) for oviposition even driven by challenges of variably light conditions and similar leaf colouration. Here, we explored this question in the oriental fruit moth Grapholita molesta, a major pest of stone fruits worldwide, using coloured squares under changing illuminants (1000, 100, 1 and 0.01 mW/m 2 ). G. molesta female preferred to oviposit on green and orange over yellow, red, blue and purple with a lower discrimination at starlight (0.01 mW/m 2 ), whereas the preferential brighter white can be discriminated clearly from those achromatic grey and black at all tested light intensities. When both cues were presented in conflicting for oviposition, the moths were more attracted to brightness than colour cues irrespective of light intensity they are exposed to. Interestingly, there was a decrease in the reflectance between young and old leaves of P. persica at similar wavelengths between 500 and 550 nm, providing an apparent brightness. Ovipositing females preferred the brighter light green over the dark green. Our results indicate that as a more reliable cue, brightness of leaves rather than colour plays a more important role for mediating crepuscular moth G. molesta to lay eggs on young leaves in microhabitats in changing light environments. We discuss that the brightness oriented in oviposition task in complex orchards is relevant to leaf apparency.

The chive gnat, Bradysia odoriphaga , is a notorious pest of Allium species in China. Colour trapping is an established method for monitoring and control of Bradysia species. In order to clarify the effect of colour preference of B . odoriphaga for the perched substrate, multiple-choice tests were used to assess the response of the chive gnat to different colour hues and brightness levels under different intensities of white illumination and two spectrally different illuminations. Given the choice among four colours differing in hue under different intensities of white illumination and two spectrally different illuminations, chive gnat adults significant preferred the black substrate, a lesser preference to brown and green substrates, and the least preference to orange substrate irrespective of illumination. Given the choice among four levels of brightness under the same illumination conditions as those in the previous experiment (different intensities of white illumination and two spectrally different illuminations), chive gnats preferred black substrate over dark grey, light grey and white substrates. Meanwhile, both virgin and mated adults significantly preferred black over other colour hues and brightness. Based on our results, we conclude that the chive gnat adults significantly prefer black substrates irrespective of colour hues and brightness. This behaviour does not alter with ambient light condition changes. No difference observed between choices of female and male adults. Our results provide new insight for understanding the colour choice behaviour in chive gnat and pave a way to improve monitoring and control of chive gnats and management.

The Oriental fruit moth, Grapholita molesta (Lepidoptera: Tortricidae), is a major pest of tree fruits worldwide, and the diapausing larvae overwinter in cryptic habitats. Investigations of overwintering G. molesta were conducted in adjacent peach, pear and apple orchards in Northern China over three consecutive winters to determine the overwintering site and habitat preferences of the moth. Counts of overwintering larvae in the different orchards demonstrated that the late-maturing peach orchard ('Shenzhou honey peach') was the most preferred overwintering habitat with more than 90% of the collected larvae. Larvae were more abundant in host trees, and they very rarely overwintered in the soil. The overwintering site preferences on the host trees were significantly different; over 50% larvae were located in the tree trunks, and followed by main branches. Most of the G. molesta overwintered on the sunny side of the host trees at or below 60 cm from the ground; a few were cocooned on the shaded sides of the trees or greater than 60 cm from the ground. G. molesta began overwintering between August and October, mid- to late September was the peak period for entering winter diapause during 2011-2013 (77.78, 67.59 and 71.15%, respectively). Our findings improve understanding of the orchard habitat and overwintering site preferences of G. molesta and would be useful in the development of efficient forecasting and pest-management strategies for orchards during the winter and early spring.

The oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), is a major pest of fruit trees worldwide. Females oviposit on the young leaves of peach [Prunus persica (L.) Batsch (Rosaceae)] shoots at twilight, when light intensity changes markedly. Previous researches have shown that the oviposition response of this moth is guided particularly by visual and olfactory cues from host plants. However, the relative importance of visual and olfactory cues in their oviposition preference is largely unknown. As a crepuscular moth, how do choices change as light intensity drops rapidly from day to night? In the present study, through two‐choice behavioural experiments, the oviposition responses of G. molesta to visual and olfactory cues (alone or in combination) from peach shoots were tested at four light intensities ranging from daylight to starlight. Grapholita molesta showed similar oviposition responses to plant cues under 1 000, 100, 1 and 0.01 mW m−2 illumination. Olfactory cues from peach shoots attracted significantly more oviposition than the negative control, whereas visual cues alone did not. Furthermore, olfactory cues were more attractive than visual cues, and no significant interaction was observed between the responses to the two cues. Our findings indicate that G. molesta females mainly rely on olfactory cues to recognize oviposition sites, regardless of differences in light intensity. These results do not provide evidence for attraction to visual cues, but the possibility that the brightness of leaves might be used to guide oviposition is discussed.

Some insects that particularly prefer sunny or shaded sites use light intensity to locate suitable oviposition sites during the day. However, it is not known whether crepuscular species can be guided by light for oviposition under dim or variable light conditions. We used the crepuscular moth Grapholita molesta (Busck) (Lepidoptera: Tortricidae), a major pest of stone and pome fruits worldwide, to investigate oviposition response to light at various intensities (1000, 100, 10, and 1 mW m −2 ). Light intensity in sunny sites in a peach tree canopy is about 10× higher than in shaded sites. In both light vs. dark and brighter light vs. darker light choices, G. molesta females can discriminate differences in light intensity, exhibiting a strong preference for brighter light, independent of light intensity. Moreover, the light-dependent oviposition responses did not change when exposed to odor stimuli. Our findings show that this crepuscular moth G. molesta can use light intensity to direct oviposition toward relatively sunny sites under dim light conditions. This study highlights the importance of vision for crepuscular species in oviposition site selection.

statement: Chive gnat (Bradysia odoriphaga) innately prefer to move to black 21 substrate irrespective of colour hues and brightness. This behaviour maintained the ambient 22 lights change. 23 24 25 26 27 High innate preference for black substrate in the chive gnat, Bradysia odoriphaga 28 (Diptera: Sciaridae) 29 Summary 30 The chive gnat, Bradysia odoriphaga, is a notorious pest of Allium species in China. Colour trapping is an 31 established method for monitoring and controlling of Bradysia species. In order to clarify the effect of 32 colour preference of B. odoriphaga for the egg-laying substrate, multiple-choice tests were employed to 33 assess the spontaneous response of the chive gnat to different colour hues and brightness levels under 34 different intensities of white illumination and two spectrally different illuminations. Given the choice 35 among four colours differing in hue under different intensities of white illumination and two spectrally 36 different illuminations, chive gnat adults visited preferably the black substrate, a lesser extent to brown and 37 green substrates, and the least extent to orange substrate irrespective of illumination. Given the choice 38 among four levels of brightness under the same illumination conditions as those in the previous experiment 39 (different intensities of white illumination and two spectrally different illuminations), chive gnats preferred 40 black substrate over dark grey, and these over light grey and white substrates. Meanwhile, both virgin and 41 copulated adults significantly preferred black over other colour hues and brightness. Based on our results, 42 we conclude that the chive gnat adults significantly prefer black substrates irrespective of colour hues and 43 brightness. This behaviour does not alter due to ambient light condition changes. No difference observed 44 between choices of female and male adults. Our results provide new insight for understanding the colour 45 choice behaviour in chive gnat and pave a way to improve monitoring and control of chive gnats and 46 management. 47 48 Key words: Bradysia odoriphaga, chive gnat, colour preference, black substrate, hue, brightness, colour 49 trapping. 50 259 An L. et al. 2018. The yellow specialist: Dronefly Eristalis tenax prefers different yellow colours for landing and proboscis260

No abstract