The male genital armature in the bees is originally composed of three pairs of tubercles, homologous with those of the female, all originally arising from three abdominal segments, two afterward being anterior, and the third pair nearer the base of the abdomen.
The ovipositor of the dragon-flies (Odonata) is essentially like that of the Orthoptera and Hymenoptera. Thus in Æschna (Fig. 196), Agrion (Fig. 196, C), and also in Cicada it consists of a pair of closely appressed ensiform processes which grow out from under the posterior edge of the eighth uromere and are embraced between two pairs of thin lamelliform pieces of similar form and structure.
The styles and genital claspers (Rhabdopoda).—Other appendages of the end of the abdomen of pterygote insects, and generally, if not always, arising from the ninth segment, are the clasping organs, or rhabdopoda as we may call them, of Ephemeridæ (Fig. 197), Neuroptera (Corydalus [Fig. 198], Myrmeleon, Rhaphidia), Trichoptera, Lepidoptera, Diptera, and certain phytophagous Hymenoptera. They do not appear to occur in insects which are provided with an ovipositor. In Thysanura the styles are present on segments 1–9 (Fig. 179). Those of the male Ephemeridæ, of which there are two pairs arising from the ninth segment, are remarkable, since they are jointed, and they serve to represent or may be the homologues of two of the pairs of stylets composing the ovipositor of insects of other orders. The lower pair (Fig. 197, rh) are either 2–, 3–, or 4–jointed (in Oniscigaster 5–jointed), while those of the upper pair are 2–jointed (rh′). These rhabdopods in the ephemerids are evidently very primitive structures, since they approach nearest in shape and in being jointed to the abdominal legs of Scolopendrella and the Myriopoda. The styles of the Orthoptera are survivals of the embryonic appendages of the ninth segment (Wheeler, etc.). In Mantis they are seen to have the same relations as the cerci, as shown by Heymons (Fig. 200).
Fig. 197.—Abdomen of Ephemera (Leptophlebia) cupida, ♂: c, base of cercopoda; rh, outer 3–jointed claspers or rhabdopods; rh′, inner pair. A, side view.
Fig. 198.—End of abdomen of Corydalus cornutus, ♂: vh, rhabdopod; c, cercopod.
In the Phasmidæ, in Anabrus, and in the Odonata the cercopods, which are not jointed, are converted into claspers, and in the Odonata the claspers are spiny within, so as to give a firmer hold. The suranal plate is apparently so modified as to aid in grasping the female. In nearly all the Trichoptera there are, besides the suranal plate, which is sometimes forked (Nosopus), a pair of superior and of inferior claspers, and in certain genera (Ascalaphomerus, Macronema, Rhyacophila, Hydropsyche, Amphipsyche, Smicridea, and Ganonema) the lower pair are 2–jointed like those of Ephemeridæ. The number of abdominal segments in the adult Trichoptera is nine, and McLachlan states that the genital armature consists of three pairs of appendages, i.e. a superior, inferior, and intermediate pair, besides the suranal plate (vestige of a tenth segment) and the penis. Judging by his figures, these three pairs of appendages arise from the last or ninth uromere, and the upper pair seem to be the homologue of the cercopoda of ephemerids. It needs still to be ascertained whether the intermediate pair is a separate set, or merely subdivisions of the upper or lower, and whether one of the latter may not arise from the penultimate segment, because we should not expect that the last segment should bear more than one pair of appendages, as we find to be the case in arthropods in general, and in the Neuroptera, from which the Trichoptera may have originated.
Fig. 199.—End of abdomen of embryo of Mantis: r, rhabdopod; c, cercopod; sp, suranal plate; st, stigma on 8th segment.—After Heymons.