Development,Behavior,Experimental Population Characteristics And Breeding Techniques Of Aphelinus Maculatus Yasnosh

The aphid parasitoid,Aphelinus maculatus Yasnosh,as Aphelinus of Aphelinidae of Hymenoptera,was first described as a new record in China in 2016,and it is a important parasitic nature enemy parasitizing on Myzus persicae Sulzer.At present,only the collection sites,two host species and adult morphology of A.maculatus have been described,but there is little literature on the biological characteristics of A.maculatus so far.In order to explore and utilize this wasp effectively,a series of biological characteristics of A.maculatus were studied in the laboratory by breeding and observing,and the theoretical basis for artificial mass reproduction and practical application is also provided.The results show that:1.Morphology and life cycle of A.maculatus and change of its hostFemale adult of A.maculatus is larger than male adult in size.The third funicle of antenna of female adult is subquadrate,but length is about 2.0 times as its width for the third funicle of antenna of male adult.Longer and stronger setae on the funicles and club of antenna of male adult.The immature stages of A.maculatus includes egg,larva and pupa,and it have three larval instars.Instars differ in shape,mandibles and respiratory spiracles.The first instar larva is elongate in shape,the second instar larva is spindle-shape,and the third instar larva is spherical with a small tail.Mandibles of the first and second instar larvae are not observed clearly,and their pharynxes are well developed.Mandibles of the third instar larva develop well and each is looked as a dark yellow sharp pointed spine projecting from one corner of a transparent broad triangular base.The third instar larva possesses seven pairs of respiratory spiracles,one pair in the mesothoracic segment and other six pairs successively in the second to seventh abdominal segments.As the development of parasitoid larva proceeds,a brown patch appears in the center of the host aphid,which is the midgut of the parasitoid larva within the host aphid,becomes larger in size and darker in color.The host aphid turns to an entirely black mummy and dies at the stage of pupa(including prepupa).The life cycle of A.maculatus from egg to adult is 11.5-14 days at the temperature of 26±1°C.2.Behavior of A.maculatus adultsA.maculatus adults emerge mainly at 6:00-10:00 am.Female and male adults can mate on the first day after emergence.The mating process can be divided into four phases:courtship,precopulation,copulation and postcopulation.The duration of copulation is short,only lasting for 5.5±0.2 s.In the 3 hours being observed,one male can copulate with 2-4 unmated females,while the female only copulate once.Mating competition occurs among females and also among males.A.maculatus can reproduce offspring by parthenogenesis and amphigenesis.Male offsprings are reproduced by parthenogenesis,but female and male offspring by amphigenesis.The parasitic process can be divided into steps such as searching host,examining host,probing insertion site,parasitic oviposition or feeding host,and cleaning and carding.The decision of parasitic oviposition or host feeding is related to the ovipositor insertion time into aphid body.When the ovipositor insertion time is longer than 4.8 min,adult wasps are more likely to feed host.A.maculatus wasps prefer to feed the early instar nymphs of M.persicae,rarely feed 4 d-or 5 d-old nymphs,but can parasitize aphids of different day-old nymphs of M.persicae.One female wasp can parasitize 14.8 aphids and feed 3.7 aphids on the average within 24h.The adult longevity is related to nutrient supplement after adult emergence.Adult wasps fed 10%sucrose or 10%honey could live 24±2.5 d and 28±1.6 d,respectively.3.The life table of experimental population of A.maculatusThe female adult of A.maculatus can lay eggs at the first day after emergence,and numbers of laying eggs decrease in a fluctuating pattern with the increase of wasp age.The peak values are 15.7,13.95,11 and 6.75 on the 5^th,14^th,20^thand 30^thdays after emergence,respectively.The mean value of longevity of female adult is25±2.76 days,and male adult is 12.67±2.08 days.The mean number of M.persicae fed by a female wasp is 52.50±5.31,and parasitized by a female wasp is271.92±31.13,and killed by a female wasp is 324.42±36.15 in the whole life of A.maculatus.Within 20 days after emergence,the female ratio of offspring changes in the range of 65%to 78%,then the female ratio of offspring begin to decline,and from 33^thdays after emergence,the offspring are all male.The net reproduction of experimental population of female A.maculatus is 163.8,the mean generation time is 22.8 d,the intrinsic rate of natural increase is 0.2236,and the finite rate of increase is 1.2505.4.Effects of temperature on development of A.maculatusA.maculatus is capable of completing its total development from egg to adult at 13 to 28?,but no adults could emerge from mummies obtained at 33?.The developmental time decreased with increasing temperature within the temperature range of 13 to 28?.Lower and upper developmental thresholds for egg-adult stage of A.maculatus are 5.59°C and 28.17?,respectively.The optimal developmental temperature for egg-adult stage of A.maculatus is 27.45?.The thermal constants for egg-prepupa,prepupa-adult and egg-adult developmental stages are estimated at121.51,127.88 and 243.90 DDs,respectively.Survival rates of different developmental stages of A.maculatus were highest at 23?ranged between 74.32%-89.16%and significantly declined at 28?.5.Artificial breeding technology of aphids and A.maculatusA key to artificially breed parasitoids is considered for breeding of host aphids.The hydroponic leave to breed aphids and parasitoids is a effective method to breed.The breeding method of A.maculatus includes following steps:plant purchase,culture medium preparation,leave cuttage and hydroponics,inoculation of aphids,aphid breeding,parasitoid breeding,parasitoid development,collection of mummies and collection of adult parasitoid.It takes about 20 days from the plant purchase to the collection of adult parasitoid,and 200,000-220,000 parasitoids are obtained,of course it can also breed in batches according to the plan.