Comparison Of The Wing Base Structures Of Panorpidae In Different Resting Postures (Mecoptera)

The most notable feature of Neoptera is that wings can fold back and are placed on the back of the abdomen at repose through the basic and special structures of the wings.Folding is an important proctection mechanism for insects and an important factor in the success of Neopterans to become the most successful group in the animal kingdom.The key to wing folding mechanism is the third axillary sclerite in the axillary area and the special muscles connected with the third axillary sclerite,namely the lateral wing folding muscles.The wing folding mechanism has been studied in depth in many insect groups.However,the research on the wing folding mechanism and the structures of the wing axillary area is still insufficient in Mecoptera.Panorpidae is the largest family of Mecoptera and is widely distributed in the mountains of the Northern Hemisphere.When the adult scorpionflies are resting,their wings have two different positions,which are flat and roof-like.What causes these two positions of scorpionflies wings has not been studied so far.In this study,Sinopanorpa tincta(Navás,1931),Cerapanorpa nanwutaina(Chou,1981),Neopanorpa longiprocessa Hua & Chou,1997,Dicerapanorpa magna(Chou,1981)(which fold their wings flat over the body at repose)and Furcatopanorpa longihypovalva(Hua & Cai,2009),Panorpa acutipennis Hua,1998,Panorpa decolorata Chou & Wang,1981(which fold their wings roof-like over the body at repose)were selected as research objects.The structures of the axillary area of wing base were investigated by light and scanning electron microscopy.We have explored the relationship between the two different wing poses and the structures of the axillary area of wing base.The results showed that the axillary area of forewing base of these scorpionflies which fold wings flat and roof-like over the body during rest consist of the following structures:tegula,the first,second,third and fourth axillary sclerite,proximal and distal median plate,axillary cord linked with mesothorax,basalare and subalare,and pleural wing process.The axillary area of hindwing base of these scorpionflies consist of the following structures: the first,second and third axillary sclerite,proximal and distal median plate,axillary cord linked with metathorax,basalare and subalare,and pleural wing process.Having compared the wing base articulations of the two different types of scorpionflies,we found that there are significant differences between the two types of scorpionflies in the length of the second axillary sclerite at the forewing axillary area and the bottom width of the first axillary sclerite at the hindwing axillary area.Therefore,we speculate that it is probably due to the differences in the length of the second axillary sclerite at the forewing axillary area and the bottom width of the first axillary sclerite at the hindwing axillary area cause the two different wing poses at repose in Panorpidae.