Relationships of Predaceous Beetles to Tropical Forest Wood Decay. Part II. The Natural History of Neotropical Eurycoleus macularis Chevrolat (Carabidae: Lebiini) and Its Implications in the Evolution of Ectoparasitoidism

The natural history and behavior of Burycoleus macu!trris Chevrolat (Carabidae: Lebiini) are recorded for the fim time. The role of this predaceous carabid beetle in tropical forest wood decay is discussed in detail. Pred:uory roles of other wood-associated carabid beetl'es are also discussed. A mimetic complex of beetles involving both larval and adult stages is shown to involve Bt~rycolous macularis. A hypothesis is offered to explain how carabid beetles evolved ectoparasitoid· ism with the life cycle of TJ.r~rycoleus macularis representing an intermediate srage between free-living larvae and true cetoparasitoidism as found in BrachitiUS ( bombardier beetl'es ) and Lebia (colorful arboreal beetles). Immature stages of certain species of Amphix (Endomychidae) are shown tO be the only food of Burycoleus macularis. Erorylidae ( Priololus sp., ?H omooolelus sp.) and Tenebrionidae (Poecilesthru sp. ) are involved in the mimetic complex with Eurycoleus. UNTIL RECENTL v, Emycolem 1/{aw/ariJ was known from only a few specimens from diStantly separated localities from Mexico co Colombia. Reichardt ( 1972) in his review of the genus recorded only 54 specimens. Another 20 specimens were collecced near Soncecomapan, Veracruz, by "Ball, Erwin, and Leech" in 1967. Ic was che discovery of these lase specimens by George E. Ball which stimulated our interest in rhe nan1ral history of the species. Ball first located the beecles on a standing cree which was covered on one side by polypore fungal braces. The beetles were hiding in cracks in che bark, between fungal braces, and under the bark, but there was no time during the expedition to engage in prorracced rearing and behavior sn1dies. Ettrycoleus macularis is a lebiine carabid, a rribe in which both rhe mimicry and ectoparasitism relationships are known. So, after six years of speculation on the possible mimetic and ectoparasitism relationships, we have discovered the nan1ral hiscory of Ettrycolem. Our continued interest in Ettrycoletu was maintained because of the beetles' coloracion and appar· em connection wirh bracket fungi. Orher lebiine species in the genera Lebifl and Lebistina are known to be ectoparasicoid in their larval stages (Silvestri I This study was supported in pan by the W alter Rathbone Bacon Scholarship of the Smithsonian Institution through funds provided for field work on wood decay in Central America. and in part by the Environmental Sciences Program of the Smithsonian lnstirution through funds provided for field work on Sarro Colorado Island, Canal Zone. 1905; Chaboussou 1939; Lindroth 1954, 1971; Balsbaugh 1967); with rhe adult stage similar in appearance co their larval hose's adult srage. With this in mind, we hypothesized that EurycoleiiJ' immature srages would be ecroparasicoids and the hose would be a fungus beetle of che family Erocylidae; we also thought chat the host, in its adult srage, would look like Eurycoleus members. Our hypothesis was wrong in prediaing simplicicy, although resting its merits did lead us in the right d irection. During our continuing study on rhe relationships of tropical forest wood decay and predaceous beetles, we'l were able to concentrate on che Ettrycolem problem for rwo weeks in 1973 and a week in 1974 on Barro Colorado Island, Canal Zone, Panama. In all stages of irs life cycle, Ettrycolem macularis is ried ro the wood decay process of smooth barked trees ( i.e., lnga, Apeiba). This relationship is described in derail below.