221 



but the respiratory and excretory functions are predominant, and also 

 that the coelom in these forms contains a nutritive fluid. 



(Schluß folgt.) 



3. On the secondary spiracles on the legs of Opilionidae. 



By J. C. C. Loman, Amsterdam. 



eingeg. 15. März 1896. 



We are indebted to the skilful investigations ofH. J.Hansen^ 

 for the discovery of spiracles on the legs of some Opilionidae. They were 

 found only in the Family of Phalangioidae Thor. , which is however 

 widely spread, species being known to exist in nearly all parts of the 

 world. In this family the tibia of each leg possesses two minute spi- 

 racles, one proximal, situated on the backside of its basis quite near 

 the patella, the second, distal one, on the fore and upper part at a 

 little distance from the metatarsus. The external opening of the spiracle 

 leads into a kind of respiratory cave of the form of a lens, situated 

 immediately beneath the skin, and the trachea opens itself through the 

 interior wall of this cave. As for the variations of position and size in 

 difl'erent genera I may refer to the description of Hansen. On the 

 whole the differences are slight. After many measurements I found 

 the average diameter of the proximal spiracle oî Phalangium opilioh. to 

 be 0,1 4 mm, that of the distal being always a little smaller, only 0,11 mm. 



The tracheal system of Opilionids, as hitherto known, consists of 

 two big tracheae originating from stigmata, situated in the groove 

 between the fourth coxa and the abdomen. Each foot receives two 

 smaller branches from the principal one, which are to be seen running 

 down the femur and the patella. One of these a little larger than the 

 other, communicates with the proximal spiracle of the tibia, whereas 

 the second passes down the tibia and reaches the distal spiracle, its 

 branches going as far as the tarsus. 



Now the tracheae of Opilionids, as far as we know or may guess, 

 are formed in early stages of development by invagination of the ecto- 

 derm, and therefore it seemed of interest to investigate whether these 

 secondary spiracles had a similar origin as the main trunks. 



So I searched after very young harvest-men during the spring of 

 1894 and 1895 and succeeded in collecting some dozens, most cer- 

 tainly belonging to different genera, probably Phalangium opilio L. 

 and Acantholophus spinosus l>osc, but, as young Opilionids differ from 

 the adult ones in nearly all systematical characters (external structure, 

 colouring:, etc.) it is impossible to determine the species, they belong 

 to, with absolute certainty. 



1 Dr. H. J. Hansen, Entomologiske Meddelelser, 1893. p. 198. 



