A growing number of studies have revealed the presence of closely related endosymbionts in phylogenetically distant arthropods, indicating horizontal transmission of these bacteria. Here we investigated the interspecific horizontal transmission of Rickettsia between two globally invasive whitefly species, Bemisia tabaci MEAM1 and B. tabaci MED, via cotton plants. We found both scattered and confined distribution patterns of Rickettsia in these whiteflies. After entering cotton leaves, Rickettsia was restricted to the leaf phloem vessels and could be taken up by both species of the Rickettsia-free whitefly adults, but only the scattered pattern was observed in the recipient whiteflies. Both the relative quantity of Rickettsia and the efficiency of transmitting Rickettsia into cotton leaves were significantly higher in MEAM1 females than in MED females. The retention time of Rickettsia transmitted from MEAM1 into cotton leaves was at least 5 days longer than that of MED. Phylogenetic analysis based on 16S rRNA and gltA genes confirmed that the Rickettsia extracted from the donor MEAM1, the cotton leaves, the recipient MEAM1 and the recipient MED were all identical. We conclude that cotton plants can mediate horizontal transmission of Rickettsia between different insect species, and that the transmission dynamics of Rickettsia vary with different host whitefly species.

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The Asian citrus psyllid, Diaphorina citri Kuwayama, is the most serious pest of citrus worldwide. It acts as a vector for a group of phloem‐limited bacteria ( Candidatus Liberibacter spp.) that causes Huanglongbing (HLB) disease. Thus, D. citri management is an important strategy against HLB, and biological control is currently considered as the most effective method because of the unsustainable and negative side effects of chemical control. Here, we isolated a new strain of entomopathogenic fungus, Cordyceps javanica (GZQ‐1), from one cadaver of D. citri adult based on its morphological and phylogenetic data. Five conidial concentrations of the C. javanica pathogen (1 × 10 3 , 1 × 10 4 , 1 × 10 5 , 1 × 10 6 , and 1 × 10 7 conidia/ml) were assessed against six life stages of D. citri (1st‐5th instar nymphs and adults). Results showed that C. javanica GZQ‐1 was highly pathogenic to D. citri nymphs (69.49%–90.87% mortality) and adults (69.98% mortality). The LC 50 and LT 50 values of C. javanica against 1st‐2nd instar (younger), 3rd‐4th instar (middle aged), 5th instar (older), and adults were 1.20 × 10 5 , 1.10 × 10 6 , 4.47 × 10 6 , 8.12 × 10 6 conidia/ml and 4.25, 4.51, 5.17, 5.49 days, respectively. Moreover, glasshouse experiments indicated that this C. javanica GZQ‐1 caused higher infection rates of D. citri adults compared to two other fungal strains we previously isolated in the laboratory, Cordyceps fumosorosea (IF010) and Metarhizium anisopliae (CNGD7).

Even though ladybirds are well known as economically important biological control agents, an integrative framework of DNA barcoding research was not available for the family so far. We designed and present a set of efficient mini-barcoding primers to recover full DNA barcoding sequences for Coccinellidae, even for specimens collected 40 years ago. Based on these mini-barcoding primers, we obtained 104 full DNA barcode sequences for 104 species of Coccinellidae, in which 101 barcodes were newly reported for the first time. We also downloaded 870 COI barcode sequences (658 bp) from GenBank and BOLD database, belonging to 108 species within 46 genera, to assess the optimum genetic distance threshold and compare four methods of species delimitation (GMYC, bPTP, BIN and ABGD) to determine the most accurate approach for the family. The results suggested the existence of a 'barcode gap' and that 3% is likely an appropriate genetic distance threshold to delimit species of Coccinellidae using DNA barcodes. Species delimitation analyses confirm ABGD as an accurate and efficient approach, more suitable than the other three methods. Our research provides an integrative framework for DNA barcoding and descriptions of new taxa in Coccinellidae. Our results enrich DNA barcoding public reference libraries, including data for Chinese coccinellids. This will facilitate taxonomic identification and biodiversity monitoring of ladybirds using metabarcoding. As species are a fundamental biological category, accurately identifying them is an essential premise of biological studies. Tautz et al. 1 proposed DNA sequences as a species identification system for the first time. Subsequently, the 5' end of the mitochondrial cytochrome c oxidase subunit I gene (COI) has been suggested as a standardized DNA "barcode" for identifying species of all groups of animals, launching the DNA barcoding technology 2. The success of barcode identification based upon genetic distances ultimately depended on differences between intraand interspecific divergences 2-4. DNA barcoding using the 658 bp 5' region of mtCOI DNA sequence as a tool, has turned out as very efficient and reliable for identifying specimens of unknown origin and taxonomic status, and also for the identification of different developmental stages. The approximately 1600 base-pairs comprise a range of different functional domains showing heterogenous substitution patterns 5,6. In addition to its utility for distinguishing known species, the COI region has also been found suitable for revealing cryptic species 7-11 , and biogeographic and phylogeographic patterns, and also species level phylogenetic relationships 12-14. The family Coccinellidae is placed in the superfamily Coccinelloidea within the Coleopteran suborder Polyphaga 15,16. Coccinellids are well known as economically important biological control agents, but this family is ecologically and morphologically very diverse. It comprises about 490 genera and nearly 6000 described species worldwide 17. Due to relatively small body size ...