Worldwide, the most two important cryptic species of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) are MEAM1 (Middle East–Asia Minor 1, “B” biotype) and MED (Mediterranean, “Q” biotype). Although both B. tabaci MEAM1 and MED are polyphagous, they differ greatly in host choice and performance on various host plants. MEAM1 prefer to settle and perform better than MED on cabbage (Brassica oleracea), for example, but the underlying mechanism is largely unexplored. In the present study, we first measured the contents of the main secondary insect‐resistant substances (glucosinolates and phenolics) and main nutrients (soluble proteins, total amino acids and total nitrogen) in five cabbage genotypes. We then examined the settling and oviposition choices of MEAM1 and MED on the five cabbage genotypes, respectively. The settling and oviposition preferences of both MEAM1 and MED were negatively related to the content of total phenolics rather than to the content of glucosinolates or main nutrients. Furthermore, our results showed that MEAM1 ranked the host quality of the cabbage genotypes more accurately than MED. The results at least in part indicate that total phenolics rather than glucosinolates mediate the host choice of B. tabaci MEAM1 and MED on the five cabbage genotypes.

MEAM1 (Middle East-Asia Minor 1, "B" biotype) and MED (Mediterranean, "Q" biotype) are the two most destructive cryptic species of the Bemisia tabaci complex on the planet. Our previous studies have shown that MEAM1 outcompetes MED on cabbage; the underlying mechanism is unknown. In the Brassicaceae family, the glucosinolatemyrosinase defense system plays a crucial role in deterring feeding, inhibiting growth, and causing acute toxicity against a wide range of generalist herbivores. In the present study, we first compared the survival of MEAM1 and MED exposed to sinigrin (a glucosinolate) and myrosinase (an enzyme that degrades glucosinolates); we found that survival of both species was high in response to sinigrin alone but was near zero in response to sinigrin + myrosinase. We then used electropenetrography (electrical penetration graphs, EPG) to assess the feeding behaviors of MEAM1 and MED whiteflies on cabbage. The EPG results revealed that the mean duration of each potential drop (pd, indicating an intracellular puncture) was substantially longer for MED than MEAM1 on cabbage, indicating that the exposure to the toxic hydrolysates of glucosinolate and myrosinase is greater for MED than for MEAM1. We therefore conclude that differences in penetrating behaviors may help explain the different effects of cabbage on MEAM1 and MED whitefly species.

Variations in species morphology and life‐history traits strongly correlate with geographic and climatic characteristics. Most studies on morphological variations in animals focus on ectotherms distributed on a large geographic scale across latitudinal and/or altitudinal gradient. However, the morphological variations of spiders living in the same habitats across different seasons have not been reported. In this study, we used the wolf spider, Pardosa astrigera, as a model to determine seasonal differences in adult body size, melanism, fecundity, and egg diameter both in the overwintering and the first generation for 2010 and 2016. The results showed that in 2010, both females and males of the overwintering generation were significantly darker than the first generation. Moreover, the overwintering females were markedly larger and produced more and bigger eggs than the first generation in both 2010 and 2016. Considering the overwintering P. astrigera experiencing low temperature and/or desiccation stress, these results suggest that substantially darker and larger body of the overwintering generation is adaptive to adverse conditions.

Two cryptic species of the Bemisia tabaci species complex, MEAM1 (Middle East-Asia Minor 1) and MED (Mediterranean), are highly destructive herbivores. Attack by herbivorous insects often induces defense responses in plants, including the accumulation of toxic secondary metabolites, the synthesis of herbivore-induced plant volatiles (HIPVs) and defensive proteins, and the release of volatile organic compounds that attract natural enemies. These defense responses, which often differ depending on the herbivore, may affect the preference and performance of later-arriving con- and heterospecific whiteflies that attack the same plant. In the present study, we found that MEAM1 whiteflies preferred settling and ovipositing on non-infested and MED-infested cabbage over MEAM1-infested cabbage plants, but that MED whiteflies showed no significant difference in settling or oviposition preference among non-infested, MEAM1-infested, and MED-infested plants. MEAM1 infestation increased the contents of total phenols and flavonoids in cabbage, which coincided with the increased expression of the following genes in the phenylpropanoid biosynthesis pathway: PAL2, C4H, and 4CL1. Soluble protein contents were also markedly higher in the MEAM1-infested cabbage plants than in the non-infested and MED-infested cabbage plants. Overall, these results demonstrate that previous infestation by MEAM1 and MED whiteflies induced defense responses in cabbage plants that had different effects on the host preference and performance of later-arriving con- and heterospecific whiteflies. Phenolic compounds may be the key factors influencing host choice by MEAM1 and MED whiteflies on cabbage plants.

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