CUTICULAR LIPIDS OF GREENHOUSE-WHITEFLY AND SWEET-POTATO WHITEFLY TYPE-A AND TYPE-B (HOMOPTERA, ALEYRODIDAE) PUPAL EXUVIAE ON THE SAME HOSTS

Cuticular lipids were extracted and chemically characterized from the pupal exuviae and associated dorsal extrusions and palisade wall of th e exuviae that are secondary structures of the greenhouse whitefly, Tr ialeurodes vaporariorum (Westwood), and from pupal exuviae of the swee tpotato whitefly, Bemisia tabaci (Gennadius), type B reared on tomato, poinsettia, broccoli, tobacco, or lettuce. The pupal exuviae of T. va porariorum separates completely at adult eclosion from its palisade wa ll (not present in B. tabaci), allowing removal of the exuviae for ana lysis of its cuticular lipids. Four classes of lipids were detected fr om all hosts in the exuviae of T. vaporariorum: paraffins, alcohols, a ldehydes, and acetates, whereas variable combinations of paraffins, al cohols, and aldehydes were detected in B. tabaci. T. vaporariorum exuv iae on all hosts had significantly more total lipids than did B. tabac i. Both lipid class and constituent abundance were influenced signific antly by different interactions of the whitefly and host plant. In the greenhouse whitefly, the four lipid classes were insect controlled an d variability within class was influenced by the host plant, whereas i n the sweetpotato whitefly type B, lipid class variability was random and directly related to host. Alcohols were the most abundant lipid fo und in T. vaporariorum, whereas no particular lipid class was consiste ntly predominant in B. tabaci. Alcohols were not detected from exuviae of B. tabaci reared on the solanaceous tomato or tobacco plants but w ere detected on B. tabaci reared on poinsettia and broccoli. The cutic ular lipids of B. tabaci type A and B on sweetpotato and cotton were c ompared and no major differences were found. Therefore, measurable dif ferences in the cuticular lipids of T. vaporariorum and B. tabaci can be used to distinguish between these two whiteflies but cannot be used to distinguish the two types of B. tabaci when reared on the same hos t plant. The composition of lipid classes and individual chemical cons tituents in the secondary structures of T. vaporariorum differed signi ficantly.