Current Research in Neuropterology. Proceedings of the Fourth International Symposium on Neuropterology. Bagntres-de-Luchon, France, 1991. Canard, M., Aspiick, H. & Mansell, M.W. (Eds). Toulouse, France, 1992. Pp. 193-202. A preliminary survey of the possible evolutionary relationships of the gonarcus-parameres complex in some Myrmeleontidae (Insecta : Neuroptera) * Emilio INSOM & Salvatore CAW] Universith di Camerino, Italy Universith di Firenze, Italy ABSTRACT The authors have studied the variability of the gonarcus-parameres complex in tribes of Neuroptera. Although the results must be deemed as preliminary and subject to revision, it is clear that this complex of more or less sclerotized structures shows considerable variability. While there is no doubt as to its usefulness as a specific- and generic-diagnostic character, some evolutionary trends are also apparent at higher taxonomic levels which may be useful in determining the phyletic relationships of tribes and families. This is particularly true, since it may be assumed that the evolution of these characters was independent of the selective demands of the environment, and therefore less liable to convergent adaptation. Key words : Myrmelwntidae, Ascalaphidae, gonarcus-parameres complex, morphology. INTRODUCTION Until now, the discussion of Myrmeleontoidea taxonomy has been based on wing venation and its possible evolution (MARKL1954 ; STANGE1970). That wing nervature is often significant is certain, but there are other structures, such as the gonarcus-parameres complex, which are certainly useful in understanding the relationships among the different Myrmeleontoidea. The selective pressures which have moulded these structures are obviously different from those which operated on the wings. While the latter were selected * This research was financially supported by grants from the Ministero dell'Universiti e della Ricerca Scientifica e Tecnologica (60 % funds). 193 for their mechanical fitness and had to keep a reticulation to support a smooth wing membrane (INSOM1991), the structures of the reproductive apparatus had to meet the requirements of a purely species-specific selection ; they were thus free to change significantly. Generally the gonarcus-parameres complex has been stu- died morphologically (TJEDER1970 ; ACKER1960 ; NEW 1989) or, usually, for identification of Neuroptera species. We have thus thought it worthwhile to study the comparative morphology of the gonarcus-parameres complex, so as to determine possible homologies between its constituent parts and to assess their possible significance in the detection of the phyletic relationships among the various genera of Myrmeleontidae. MATERIALS AND METHODS The genera studied are listed in Table I. The last abdominal segments of the specimens studied were investigated both by optical microscopy (OM) and by scanning electron microscopy (SEM). For the purpose of OM examination, the tip of the abdomen of the specimens was first soaked in hot water with the addition of some drops of NH40H. The last segments were then removed and : i) transferred to hot lactic acid for about 10 min, ii) rinsed with distilled water, iii) moved to a hot water solution of 10 % KOH for about 10-15 min, iv) rinsed again with dis- tilled water and v) transferred to Faure's fluid without arabic gum, where they were studied. Some specimens were lightly stained with Chlorazol black E in or- der to highlight the membranous structures. The specimens were finally stored in glycerol 84-88 %. For the SEM study, the segments were : i) rehydrated, ii) cleaned, iii) dehy- drated by the usual alcohol series, iv) moved to amylacetate, v) moved to the cri- tical point-drying Euroscop CPD 750@ apparatus, and vi) coated with gold in an Agar Aids@ sputter coater. Observations were made at lOkV with a Stereoscan 200@ (Cambridge Instruments Ltd) scanning electron microscope. DESCRIPTIONS OF STRUCTURES On the evidence of the material studied, we can now distinguish at least six gonarcus-parameres complex types (Table 11) : 1. Type A (Palparini, Stilbopteryginae, Ascalaphidae partim) ; 2. Type B (Myrmelontini) ; 3. Type C (Isoleontini [Nemoleontini] : Cueta (NavBs, 1911) ; 4. Type Dl (Myrmecaelurini) ; 5. Type D2 (Distoleontini) ; 6. Type E (Acanthaclisini) . Type A. This type has a well-developed and sclerotized gonarcus (Palpares Ram- bur, 1842 ; Pseudopalpares Insom & Cafii, 1988 ; Parapalpares Insom & Carfi, 1988 ; Nosa NavBs, 1912 ; Indopalpares Insom & Cad, 1988). In only a few instances does it show a tendency to become membranaceous (Trichocercus Insom & Carfi, 1988 ; Goniocercus Insom & Ca&, 1988). Caudal to the gonarcus there Male genitalia of Myrmeleontidae are the parameres separated by the pelta, which is usually well-developed. It is suprising how very similar morphologies of this type are to be found in both the Palparini and in at least two tribes of Ascalaphidae (Suhpalacsini and Encyoposini) and in the subfamily Stilbopteryginae as shown by KJMMINS(1940), ACKER (1960) and NEW(1982). Table I. Distribution of gonarcus-parameres complex types in some tribes of Myrmeleontidae. Genera asterisked (*) were studied by the authors ; the other genera are quoted from authoritative descriptions. Epacanthacl~sis Okamoto. 1910 Dendroleontlnl Dendroleon Brauer. 1866 I I Afghanoleon Holzel. 1972 * Acanthaclls~s Rambur. 1842 Acanthacl~slnl * Syngenes Kolbe, 1897 * Centrocl~s~sNavbs. 1909 * Nophls Navbs, 1912 Aspoecklna Holzel, 1969 Myrmecae lurlnl * Myrmecaelurus Costa. 1855 Nohoveus Navbs, 1919 LoPezus Navbs. 1913 * Iranoleon Holzel, 1972 Maracanda McLachlan, 1875 Sol ter Navhs. 1912 * Gepus Navbs, 1912 Ge~ellaHolzel, 1968 Isoleon Esben-Petersen. 1930 * Cueta Wavhs, 1911 * Euroleon Esben-Petersen. 1918 Myrmeleontini * Hn-meleon L. 1767 I Morter Navhs, 1915 Mesonernurus Navbs, 1919 Geyra Esben-Petersen, 1920 Myrme leontinae * Macronernurus Costa, 1857 Pignatellus Navhs, 1914 Quinemeurus Kinmins. 1943 Gangui l us Navbs, 1912 Deutoleon Navbs. 1927 Distoleontini Barreja Navhs. 1915 D 2 Graonus Navbs, 1922 * Nemoleon Navhs, 1909 * Neuroleon Navbs, 1909 Nicarinus Navbs, 1914 Pseudoformi cal eo Wee 10, 1909 Creoleon Tillyard, 1918 * Distoleon Banks. 1910 Indofanes Banks, 1940 Nedrol edon Navhs, 19 14 Hegistopus Rambur, 1842 Gnmocnemia Schnelder, 1845 * Palpares Rambur, 1842 * Parapalpares Insom 6 Carfi, 1988 * Tri chocercus I nsom h Carf i , 1988 " Goniocercus Insom h Carfi, 1988 Pseudopalpares lnsom h Carfl. 1988 Indopalpares Insom b Carfl. 1988 Pamares Mansell. 1990 * Nosa Navbs. 1911 * Stenares Hagen, 1866 Table 11. Schematic arrangements of different gonarcus-parameres complex types (A-E) in tribes and families resulting--. in groups of pseudoaedeagus structures (1-111). A = Palparini (Myrmeleontidae) ; Stilbopteryginae ; ~uh~alacsini;-~ncio~osini (~scala~hidae).- B = Dendroleontini, Myrmeleontini. C = Nesoleontini (Isolwntini partirn). Dl = Myrme- caelurini. D2 = Distoleontini. E = Acanthacliiisi. G = gonarcus ; 1.m. = lamina medialis ; L.s = lamina subterminalis ; M = mediuncus ; P = parameres ; p.a. = pro- cessus apicalis ; Pt = pelta. The structures that form the pseudoaedeagus are : i) gonarcus (G) which is usually the larger structure, ii) parameres (P) either fused or partly fused with the gonarcus though their line of suture is usually quite clear, iii) pelta (Pt) arranged caudally between the two parameres, and covered by many setae. Male genitalia of Mynneleontidae For us, this condition appears the most generalized. It is obvious that this structure differs in its morphological details, and therefore the gonarcus-parame- res complex can appear different from this type. However, by careful observation it can always be placed in type A, for instance : gonarcus alone (Nosa), or gonar- cus and parameres entirely fused together (Stenares Hagen) (INSOM& CARF~ 1988). Type B. Its component parts are not fused to each other, but are united by mem- branes. The gonarcus always maintains its dorso-lateral position, while the para- meres are ventro-lateral and caudally directed ; sometimes distally there is a mediuncus (M). In Myrmeleontini the two parameres have cranially directed apo- physes that are not united with each other. The pseudoaedeagus is neither as well nor as strongly developed as in type A. Type C. So far found only in Cueta [Tribe Nesoleontini sensu MARKL(1954), HOLZEL(1969) ; Isoleontini sensu HOLZEL(1972)l. It has a rather complicated structure. We maintain that only the gonarcus may be really homologous with the so-called structures in the two above-mentioned types ; the gonarcus can be saddle-shaped or dorsally straight, as can be clearly observed in the works of HOLZEL(1969, 1972, 1982, 1983) ; the parameris, or rather the structure so na- med by various authors, is single, without any sign of original duplication. Caudal to the gonarcus, we notice the mediuncus and another accessory structure, and we maintain that it may, instead, correspond with the true parameres. This structure has an internal apophysis, lamina medialis (l.m), which is cranially directed (Fig. 1). Type Dl. This is typified by a well developed gonarcus, which may be either ap- proximately cylindrical, thin and with a wide base (Mymcaelurus Costa, 1855 ; Nophis NavBs, 1912 ; Nohoveus NavPs, 1919) or short and wide (Zranoleon Hijl- zel, 1968) ; in both instances, the parameres are small and end in two small sharp upwardly pointing protuberances. Type D2. This type appears to be directly derived from Dl. The gonarcus is much reduced and dorsally becomes a thin bridge,