Distributional Characteristics Of Phoretic Mites On The Body Surface Of The Red Palm Weevil Rhynchophorus Ferrugineus (Olivier) In Fujian Province And Their Effect On Host Flight Ability

The red palm weevil(RPW),Rhynchophorus ferrugineus(Olivier)(Coleoptera: Curculionidae,Rhynchophorus),is one of the most serious invasive pests of palm plants.It is important to investigate the relationship between mites and R.ferrugineus for future biological control work.In this study,we first investigated the phoretic mite species and quantities on the body surface of R.ferrugineus in Fujian Province.Secondly,the spatial pattern of the phoretic mites were clarified.Lastly,we explored the influence of the attachment of dominant phoretic mite Centrouropoda almerodai on the flight ability of R.ferrugineus.Results are summarized as below:(1)There was a close relationship between the R.ferrugineus and their phoretic mites.The prevalence of phoretic mites infestation was80.65%.The mean phoretic mites load on R.ferrugineus was 387.04,the mean phoretic mites load on males and females did not differ significantly.There were 9 species of phoretic mites on R.ferrugineus,including 4 species of the Uropodidae,3 species of the Histiostomatidae,1 species of the Laelapidae and 1 species of the Digamasellidae.As the dominate species,the mean adhesive rate and number of phoretic mite C.almerodai was 200.14 and 83.75%.The number of phoretic mites was different within five aeras with the largest number of mite species found in Fuzhou(8 species).The C.almerodai?Curculanoetus sp.and one miteof the Uropodidae were isolated in all areas.All mites collected were hypopus,indicating that R.ferrugineus is an important carrier for phoretic mites.(2)All phoretic mites on R.ferrugineus fitted aggregated distribution.The distribution of phoretic mites were found varied depending on adherent section of R.ferrugineus.U.orbicularis and U.javae were observed on the thorax and foot,while other mites were found on the inner space of the elytra of R.ferrugineus(inner surface of the elytra;membrane wing).The C.almerodai occupied the minimum spatial ecological niche index(0.17)but maximun temporal ecological niche index(2.03).The maxmum spatial ecological niche index came from Curculanoetus sp.(1.02)while the minimum temporal ecological niche index(0.24)from Proctolaelaps sp.Some phoretic mites such as C.almerodai and one mite of the Uropodidae shared a great similarity in the use of temporal and spatial resources and had the highest niche overlap index(0.95 and 0.89 respectively).The peak period of most of phoretic mites was coincided with R.ferrugineus.However,some mite species adjusted the adhesive location and dispersal time in order to reduce competitive pressure with other mite species.(3)When the phoretic mites load was 101-200 and 201-400,the flight rate of R.ferrugineus decreased significantly(34.29% and 35.45%,respectively),and the flight rate was 40.57% when the phoretic mites loadwas 0.When the phoretic mites load was 1-100,R.ferrugineus had the maximum cumulative flight distance(3.84 km/24 h),while larger phoretic mites load(201-400)decreased the cumulative flight distance significantly to 1.92 km.The mean speed of the RPW within different phoretic mites load did not have significant difference,with a range from2.02 km/h to 2.29 km/h.When the phoretic mites load was 0,R.ferrugineus had the mean maximum flying speed(3.43 km/h).When the phoretic mites load was 101-200,the mean maximum flying speed(2.74km/h)was significantly lower than others.The flying ability of R.ferrugineus decreased with the increase of the number of mites on the body surface,but a small number of mites would not affect the flying ability of R.ferrugineus.