The exciting cause of the hypertrophy, in the case of the typical galls, appears to be a minute quantity of some irritating fluid, or virus, secreted by the female insect, and deposited with her egg in the puncture made by her ovipositor in the cortical or foliaceous parts of plants.
The typical insectan ovipositor with its three pairs of processes, one pair belonging to the eighth and two pairs to the ninth abdominal segment, can be distinguished in the female.
The sting of wasps, ants and bees is a modified ovipositor and is used for egg-laying by the fertile females, as well as for defence.
There are two families of Terebrantia: (a) the Aeolpthripidae, whose feelers have nine segments; whose wings, relatively broad and rounded at the tip, have a few cross nervules, and whose ovipositor is curved backwards; and (b) the Thripidae, whose feelers have six to eight segments, whose narrow acuminate wings have no cross nervules, and whose ovipositor (fig.
The cerci are nearly always joined, and a typical insectan ovipositor with its three pairs of processes is present in connexion with the vagina of the female.
The morphology of the abdomen, ovipositor and genital armature is dealt with by K.
The constriction of this segment and its very perfect articulation with the propodeum give great mobility to the abdomen, so that the ovipositor or sting can be used with the greatest possible accuracy and effect.
This flexible tube is the functional ovipositor, the typical insectan ovipositor with its three pairs of processes (see Hexapoda) being undeveloped among the Coleoptera.
Jointed cerci always present; ovipositor well developed.
The ten thousand known species included in this group agree with the Cynipoidea and Chalcidoidea in the position of the ovipositor and in the jointed trochanters, but are distinguished by the fore-wing possessing a distinct stigma and usually a typical series of nervures and areolets (figs.