The ejaculatory duct is ectodermal in origin, and therefore cuticle-lined. Tenebrio is an example of an insect with both sorts of accessory glands. Testes are made up of follicles or testis tubes. These are shown in the next figure. Testes of some insects, such as Tenebrio shown earlier are a series of lobes, each of which contains follicles.
Some beetles have over a dozen lobes in each testes.
Often follicles are connected to the vas deferens by a short tube called vas eferens, as shown. In other cases, particularly in Lepidoptera, follicles are not completely separated and they share a common opening to vas deferens. Usually vasa deferentia dialate, or widen, to form the seminal vesicle just before joining the ejaculatory duct. The next figure shows a testis follicle. In the far end of follicles is the germarium.