A Text-book of Entomology / Including the Anatomy, Physiology, Embryology and Metamorphoses of Insects for Use in Agricultural and Technical Schools and Colleges as Well as by the Working Entomologist

by A. S. Packard

Fig. 345.—A, section of urinary tube of Periplaneta; B, part of tube of Perla; p, peritoneal membrane; c, cavity or lumen; n, nucleus of a secreting cell.—After Schindler.

In the larvæ of some insects the blind ends of the tubes are often externally bound to the rectum, in the silkworms being attached by fine threads to the intestine, while in some flies (Tipula and Ctenophora), two vessels may unite to form a loop. In all larval Cecidomyiæ, the two tubes are united to form a loop which curves backward, opening near the vent, the proctodæum being very short. (Giard.)

Fig. 346.—Portion of a urinary tube of Calliphora vomitoria: tr, trachea; l, lumen; k, nucleus.—After Gegenbaur.

While usually the urinary vessels form simple tubes, in many species of Lepidoptera and Diptera they are branched, thus resembling those of spiders and scorpions. Moreover, in many Lepidoptera and Diptera (Fig. 308), the tubes are not simple, but are lobulated, and in some Hemiptera (Pentatoma, Notonecta, and Tettigonia) are twisted or lace-like. In rare cases there are two kinds of urinary tubes; in Melolontha vulgaris, two of them are partly lobulated and yellow, while the other two are simple and white. Their color in beetles varies, some being whitish or yellowish; in Geotrupes, Dyticidæ, Hydrophilidæ, etc., reddish brown; in Gryllotalpa as well as Locusta viridissima, there are two different kinds of vessels, differing in contents and in color (white or yellow), as well as histologically. (Schindler.)

The exterior of the tubes is richly provided with tracheæ, which often form a web around them, and the fine branches often seem to attach them to the intestine. In Acheta they are enveloped by a very delicate, loose network of muscular fibres. (Schindler.)

The urinary tubes consist, according to Schindler, of at least three cellular layers (Fig. 345):—

1. An external, connective, nucleated membrane, the peritoneal membrane.

2. A very delicate homogeneous basal membrane, the tunica propria.

3. A single layer of large polygonal excretory cells.