Study On Comparative Morphology Of The Mealybugs (Hemiptera:Coccoidea:Pseudococcidae)

Mealybugs have tiny body and hidden life,sucking sap from plants and being serious pests of agriculture and forestry.The classification of the scales is mainly based on the morphological characteristics of adult females,and the study on the instar nymphs is relatively less.Based on the references and slide specimens,this paper mainly focused on the variation of the morphological characteristics of adult females,in which we analyzed the classification value of each feature,combined the evolution of classification features with the growth of instar nymphs,summarized the common features of all ages,and finally evaluated the importance of each morphological characteristic.1.By the comparative analysis of morphological characteristics of adult females,we summarized the variable types of different characteristics,drawn 13 pictures of the part morphological characteristics and analyzed the stability of each variation.The results are as follows:(1)The better classification features of female adults are the number of antennal segments,development or absence of legs,absence or distribution of translucent pores on hind legs,tarsal digitules knobbed or setose,absence or distribution of quinquelocular disc pores,types and distribution of multilocular disc pores,absence or distribution of tubular ducts,cluster of pores and ducts,number of cerarii,structure of anal cerarius,anal lobe bar present or absent,number of ostioles,number and distribution of circulus,types of anal ring and conical setae.(2)Some classification characteristics can be used to distinguish similar species which has no stable variation,but there is distinct difference among the species.They are the number of fleshy bristle on the top two antennal segments,the ratio of length and width of labium and the number of setae on labium,number and distribution of the single pores,number and distribution of the tubular ducts,the trilocular pores and setae on the lip of ostioles,the ratio of length of anal setae and diameter of anal ring,types and number of setae.(3)Some else characteristics have no significant variation among various groups,which generally not be used to classify.These are the length of each antennal segment and the number of setae on antennal segments,the number of labium segments,knobbed claw digitules,distribution of trilocular pores and thoracic spiracles.2.Throuth the study of evolution characteristics on 34 species of mealybugs in each instar,we elaborated the evaluation of the characteristics from first instar nymph to adult female,and the newly features in second,third instar nymph and female adults,and characteristics relatively stable in each instar.In the end,the features of each stage were summarized in the table.Results as follows:(1)The general characteristics of each instar are summarized,especially the newly features in each stage.Meawhile,we summarized the diagnosed features of the Phenacoccinae and Pseudococcinae,and drawn the morphological comparison diagram.(2)The evolution of each feature along with the instar growth were summarized.The number of antennal segments,structure of the anal lobe cerarius and the number of pores and ducts developed along with the evolution of instar nymphs.The ratio of the length of tibia and tarsus of hind legs were statistically analyzed,which present a stably creasing change.Some characteristics maintained relatively stable in each instar.This research basically clarified the variation of characteristics in each instar stages.