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LABANDEIRA—PREDATORS, PARASITOIDS, AND PARASITESlarvae are assumed to have been predaceous, basedon descendant taxa. There is little direct evidencefor freshwater predation, though the immatures ofOdonatoptera and Ephemeroptera, if aquatic in thePaleozoic (Rohdendorf and Rasnitsyn, 1980), werelikely predaceous.During the Mesozoic, more derivedodonatopteran lineages—representing about 80families and subsumed within the extant high-rankedsubgroup, Odonata—replaced the Late Paleozoicand Early Mesozoic lineages (Bechley, 1996;Bechley et al., 2001). This diverse fauna is preservedin the Solenhofen Limestone of southern Germany(Barthel et al., 1994) and similar Mesozoic deposits.Additionally, insectivorous brachyceran Diptera—such as Rhagionidae (snipe flies), Asilidae,Empididae (dance flies), and others—became aerialpredators during the later Mesozoic. This expansionaccompanied the diversification of dipteranmouthpart types, which involved modifications ofthe mandibular, maxillary, and hypopharyngealstylets, as well as the tracheation and dentition ofthe labellum. These changes provided several newways to secure, process, and consume prey. At thesame time, Mesozoic hexapod predators dwellingon the ground were dominated by the Mantodea,neuropteroids, and the superfamilies Caraboidea,Staphylinoidea, and Elateroidea among theColeoptera. Later, during the Cretaceous, vespoidwasps and ants became important ground predators.Among the first well-substantiated predators infreshwater ecosystems were nepomorph Hemipteraand caraboid Coleoptera during the latest Triassicto early Jurassic; these clades undoubtedly subsistedon a trophic base of other, perhaps herbivorous,arthropods (Ponomarenko, 1996). This Mesozoicarray of freshwater and terrestrial predatorsessentially persisted into the Cenozoic, judging bythe geochronologic ranges of major family-level taxa(Labandeira, 1994). Recent evidence, however,indicates a significant diminution of herbivoroustaxa at taxonomically lower levels at theCretaceous-Paleocene boundary in the WesternInterior (Labandeira et al., 2002; cf. Labandeiraand Sepkoski, 1993). This would have significantlyimpacted the herbivore component of food webstructure; and based on theoretical (Dunne et al.,2002) and empirical (Godfray et al., 1999) data,should translate to significant decreases intaxonomic diversity. This impoverishmentprobably cascaded upward to trophically dependentpredators, parasitoids, and parasites.Parasitoids.—One of the biggest transitions incontinental carnivory was the rather rapidappearance of major parasitoid taxa during theMiddle Jurassic to mid-Cretaceous. Of the 74parasitoid families recorded in Figure4, 57 (or 77percent) are Hymenoptera, 12 (16 percent) areDiptera, and the remaining 5 (7 percent) representPlanipennia, Coleoptera, and Lepidoptera. In theHymenoptera, the overwhelming presence ofsawflies (Symphyta) plus seven superfamilies ofapocritan and aculeate lineages (Gauld and Boulton,1988), as well as the superfamilies Tabanoidea,Asiloidea, Empidoidea, Muscoidea, and a few otherlineages in the brachyceran Diptera, truly records amajor shift in the mode of carnivory within terrestrialecosystems (Fig. 4). In the post-Triassic fossilrecord, evidence for parasitism comes fromtaxonomic assignments (Rasnitsyn, 1988), thepresence of small parasitoid emergence holes infossil pupae (Bown et al., 1997) (Fig. 2N), orteratologies of adult insects in amber (Poinar andPoinar, 1999), such as an exceptional case of abraconid larva preserved in the act of emerging froman adult ant (Poinar and Miller, 2002). The transitionto parasitoidism was accomplished by modificationsin the reproductive biology of numerousholometabolous lineages (Godfray, 1994). For theHymenoptera, an important structural change wasthe transformation of a laterally compressed,sawtooth ovipositor—designed for slicing planttissues—into a needle-like piercing or drillingmechanism with a circular cross-section. Thisstructure, initially used for inserting eggs intowood, was transformed into a device for puncturingendophytic larvae—a key innovation for basalparasitoid taxa (Rasnitsyn, 1988). An analogousstructure is the highly telescoped posteriorabdomen of the Diptera. The second importantdevelopment in early parasitoids was a shift inlarval food source, from less nutritious plant tissues229