546 



PSYCHE. 



[November 1893. 



organs of the Tenthredinidae, a family 

 •which promises to throw considerable 

 light on the ancestral peculiarities of 

 the order. 



Diptera. In these very highly 

 modified insects the number of Mal- 

 pighian vessels shows a constancy that 

 contrasts strikingly with the variations 

 occurring in the Hy menoptera : with 

 very few exceptions the Diptera have 

 in all their stages only 4 urinary tubules. 

 Still there seems to be considerable 

 variation in the manner, of their opening 

 into the intestine. Schindler* claims 

 that in Aphaniptera, Pupipara, Tip- 

 ulidae, Asilus, Haematopota, Eris- 

 talis, each of the vessels has a separate 

 opening. In Hippobosca, Musca, 

 Sarcophaga, Anthrax, Conops, Oestrus 

 and Syrphus, the vessels are united • in 

 pairs and open by means of two ducts, 

 a condition which reminds one of the 

 Gryllidae. In Tipula and Ctenophora 

 the terminal ends of the vessels are fused 

 in pairs. 



There is, I believe, some evidence in 

 favor of the view that 4 is not the 

 primitive number of vessels in the Dip- 

 tera, and that there has taken place 

 throughout the group a reduction 

 similar to what was observed in Melo- 

 lontha. I base this conclusion on an 

 observation first made by Voeltzkowf 

 and more recently confirmed by 

 Graber. % Voeltzkow describes and fig- 



* 1. c. p. 642 et seq. 



t Entwickelung im ei von Musca vomitoria. Arb. 

 zool. zoot. inst. Wiirzb. bd. 9, heft. 1, 18S9, p. 32. 



X Vergleichende studien iiber die embryologie der 

 insecten u. insb. d. Musciden. Denkschr. math. wiss. 

 classe k. akad. wiss. Wien. bd. 56, 18S9, p. 37-38. 



ures 3 pairs of tubular diverticula to 

 the proctodaeum of Musca. Two of 

 these pairs he designates as Malpighian 

 vessels, to the third pair he refers as 

 •'neuauftretende gauge." Graber's fig. 

 76, taf vii, shows that one of the "gange" 

 arises between the two Malpighian ves- 

 sels on either side. Why may not this 

 median pair of diverticula, which are 

 apparently purely embryonic structures, 

 represent a third pair of Malpighian 

 vessels ? 



There is also another fact which 

 vaguely points to a primitively hexa- 

 nephric condition in the Diptera. I 

 allude to Culex and Psvchoda, forms 

 which, according to Dufour* Raschkef 

 and Schindlerj have five Malpighian 

 vessels. This number, which, to my 

 knowledge, has been observed in no 

 other insects, may have originated from 

 the hexanephric condition either by the 

 suppression of a single tubule or by the 

 fusion of a pair of tubules into one. 

 That the latter is probably not the case 

 follows from Schindler's statement : 

 ••Dass das 5 gefiiss nicht etwa das 

 product der concrescenz zweier gefasse 

 ist. scheint mir zur geniige daraus 

 hervorzugehen, dass ich bei kleinen und 

 kleinsten larven, bei der puppe und dem 

 imago von Culex pipiens und C. annu- 

 latus immer 5. in ihren langs- und 

 breite-dimensionen einander vollstiindig 



* Memoire sur les vaisseaux biliaires ou le foie des 

 insectes. Ann. sci. nat. 2° ser. torn, xix, 1S43, P- l( >6. 



t Die larve von Culex nemorosus. Ein beitrag zur 

 kenntniss der insecten-anatomie u. histologic. Arch, 

 naturg. S3 J :)hr S- lSS 7- 



\ 1. c. p. 642. 



