Comparative Study On External Morphology Of Tetranychus Turkestani(Ugarov & Nikolskii)and Tetranychus Truncatus Ehara

Tetranychus turkestani（Ugarov&Nikolskii）and Tetranychus truncatus Ehara（Trombidiformes:Tetranychidae）are important pests in China.In this paper,the external morphological characteristics of the eggs,larvae,nymphs and adults of T.turkestani and T.truncatus are studied by using light microscope and scanning electron microscope.It enriches the ontogenetic morphological contents of these two spider mites.The main results are as follows:1.Egg:The eggs of these two spider mites are spherical,the surface of the egg shells are smooth without any special structure and there is no difference in size.But as the embryo develops,the eggs of T.turkestani tend to be yellow,while the T.truncatus eggs tend to be red.2.Larva:The larvae of these two spider mites are rounded,with three pairs of legs.The morphological structure of the gnathosoma of these two spider mites is very similar.The striae between the dorsal setae v₂ and c₁ is semiorbicalar,the striae between the dorsal setae c₁ and f₁ is transverse,and no integumentary lobes on the back.The end of empodium is split into three pairs of acicular hairs,and the number of setae in each leg is the same.3.Protonymph:The protonymphs of these two spider mites are oval,with four pairs of legs.The morphological structures of both gnathosoma and empodium of these two spider mites are very similar,and the number of setae in the dorsal,ventral and each leg is consistent.The difference is that the striae between the dorsal setae v₂ and c₁ of T.truncatus has semi-oblong integumentary lobes.4.Deutonymph:The deutonymphs of these two spider mites are oval,with four pairs of legs.The morphological structures of gnathosoma,integumentary,lobes and empodium of these two spider mites are very similar,and the number of dorsal setae and ventral setae is consistent.The number of setae of these two spider mites in legs Ⅲ and Ⅳ is the same,but the number of setae of the legs Ⅰ and Ⅱ is different.The femur I of the deutonymph of T.turkestani has five tactile setae,tibia I has nine tactile setae and one solenidion,femur Ⅱ has four tactile setae,tibia Ⅱ has six tactile setae.The femur Ⅰ of the deutonymph of T.truncatus has six tactile setae,tibia I has seven tactile setae and one solenidion,femur Ⅱ has three tactile setae,tibia Ⅱ has five tactile setae.5.Female adult:The female adults of these two spider mites are oval,with four pairs of legs.The morphological structures of gnathosoma,duplex setae and empodium of these two spider mites are very similar,and the number of setae in the dorsal,ventral and each leg is consistent.The difference is that the integumentary lobes between the dorsal setae c₁ and f₁ of T.turkestani are triangular,semicircle or semi-oblong,while the integumentary lobes of T.truncatus are semicircle or semi-oblong.The lyrifissures of T.turkestani are more pronounced,while the lyrifissures of T.truncatus are not obvious.The morphology and position of the genital opening,copulatory pore,anal opening and genital flap of these two spider mites are basically the same,but different from the T.turkestani,there are many granules on the epidermis above the genital area of T.truncatus.6.Male adult:The male adults of these two spider mites are diamond-shaped,with four pairs of legs.The morphological structures of gnathosoma and integumentary of these two spider mites are similar,and the number of setae in the dorsal,ventral and each leg is consistent.But there are many differences:The palpfemoral setae of T.turkestani male adult are spur-like,its end is obtuse,the surface is smooth,while the end of palpfemoral setae of T.truncatus is very sharp.The terminal knob of aedeagus of T.turkestani is large,and there is an obvious angle on the posterior projection near the 1/3 region.While the terminal knob of aedeagus of T.truncatus is tiny,the dorsal edge is truncated,and there is a depression at the end of 1/3.The empodium Ⅰ of T.turkestani consists of a claw-like structure with a strong mediodorsal spur,and the end of empodium Ⅱ is split into three pairs of acicular hairs.However,the empodium Ⅰ of T.truncatus is coarsely toothed,abaxially with a strong mediodorsal spur,and the end of empodium Ⅱ is split into three pairs of acicular hairs,abaxially with a mediodorsal spur.Through the comparative study of the external morphology of eggs,larvae,protonymphs,deutonymphs,female and male adults of T.turkestani and T.truncatus,we found that:From the larva to protonymph stage,they can be distinguished by the number of ventral setae and legs.From the protonymph to deutonymph stage,they can be distinguished from the integumentary pattern between the dorsal setae e₁ and f₁,ventral setae and leg setal number.And from the deutonymph to adult stage,they can be distinguished from the shape of integumentary lobs between the dorsal setae e₁ and f₁,ventral setae and leg setal number.