PSYCHE. 



THE PRIMITIVE NUMBER OF MALPIGHIAN VESSELS IN 



INSECTS.— III. 



BY WILLIAM MORTON WHEELER, PH.D., CHICAGO, ILL. 



Orthoptera. It is in this order 

 that we first meet with facts having a 

 decided bearing on the question under 

 consideration. I have no data on the 

 embryology of the Phasmidae and Man- 

 tidae.* The other families maybe taken 

 up in order. 



Blattidae. In the embryo Phvllo- 

 dromia germanica I find four Malpig- 

 hian vessels which arise as discrete 

 outgrowths of the hind-gut in the 

 manner so often described for other 

 insects. Somewhat later two more 

 vessels are added. The adult Phyllo- 

 dromia and Periplaneta orie?italzs\\nve 

 60-70 vessels according to Schindlerf 

 and Miall and Denny. J Hence a great 

 increase in the number of tubules must 

 take place during larval life. That this 

 is the case was shown by Schindler, § 

 who found only 16-18 vessels in a larval 

 Periplaneta not quite 10 mm. long, and 

 only eight vessels in larvae measuring 

 4-5 mm. Notwithstanding this increase 

 in the number of vessels, the number 



* Leon Dufour. Recherches sur les Orthopteres etc., 

 p. 35S, claims the number of Malpighian vessels in the 

 adult Mantis to be "une cehtaine environ." 



t 1. c. p. 607. 



\ The structure and life-history of the cockroach (Peri- 

 planeta orientalis) London, 1SS6, p. 12S. 



§1. c. p. 607. 



(6) persists throughout life, since, as 

 Miall and Denny* have shown, the 

 vessels of the adult are grouped in six 

 clusters at the anterior end of the strik- 

 ingly hexagonal rectum. 



Locustidae. In the embryo Xiphi- 

 dium ensiferum four Malpighian 

 vessels arise as in Blattids ; to these a 

 third pair is soon added. In the adult, 

 of which I examined four specimens, 

 the vessels are inserted in six clearly 

 defined clusters, each containing about 

 7 or S'tubules. Hence there can be no 

 doubt that in this form also the number 

 of vessels increases during larval life. 

 •This increase is probably effected by a 

 budding out of new vessels from the 

 proctodaeal wall at the bases of the em- 

 bryonic vessels. A large adult Orchel- 

 imum which I examined showed the 

 same arrangement of Malpighian ves- 

 sels as Xiphidium. 



Other writers have observed the clus- 

 tered arrangement of the excretory 

 tubulesjin the Locustidae but they fail 

 to find six clusters. According to Leon 

 Dufourt the 10-12 vessels of Ephip- 

 pigera open into the gut on five sepa- 



*1. C. 12}. 



t 1. c. p. 350. 



