510 



PSYCHE. 



[September 1893. 



Anoplotermes bleibt die zahl der 

 harngefasse zeitlebens auf 4 be- 

 schrankt." According to Nitscb* Psocus 

 bas 4 urinary tubules and authors 

 ascribe the same number to the Mal- 

 lophaga, according to Schindler. f 

 Thus, although tbe number 6 occurs 

 among the Corrodentia, tbe number 

 4 appears to be tbe more typical. 



Thysaxoptera. In his admirable 

 anatomical monograph of this order, 

 Jordan \ ascertains the number of 

 Malpigbian vessels to be 4 ; 2 extend 

 into the thorax, while the remaining 

 pair lie coiled in the abdomen. 



Rhynchota. In Aphides Malpig- 

 hian vessels were not seen by 

 Schindler. § Nor do I find any men- 

 tion of these organs in Will's em- 

 bryology of the viviparous forms. || 

 LeydigH found a single pair of 

 vessels in the Coccid Lccani2tm Jies- 

 ■peridum and Mark* * demonstrated 



*Uberdie eingeweide der biicherlaus, etc. Mag. f. 

 entomol. iv, 1S21, p. 277. 



f 1. c. p. 604. 



% Anatomie und biologie der Physapoda. Zeitschr. 

 f. wiss. zool. bd. 47. iSSS, p. 576 and 57S. 



§ 1. c. p. 639. 



|| Entwicklungsgeschichte der viviparen Aphiden. 

 Spengel's Zool. jahrb. abth. f. mat. u. ontog. bd. iii, 

 18SS. 



IT Zur anatomie von Coccus hesperidum. Zeitschr. 

 f. w'ss. zool. bd. v. 1S54, p. 3. 



* * Beitrage zur anatomie u. histologic der pflanzen- 

 laus insb. der Cocciden. Inaug. dissert. 1876 p. 52 et 

 seq. 



their occurrence in other species of the 

 same group. 



All other Rhynchota have 2 pairs, 

 which show some interesting varia- 

 tions, tabulated by Schindler.* In 

 most genera the vessels end blindly, 

 but in others (Nepa, Velia, Gerris, 

 Capsus, Cimex) the ends of the pairs 

 are united in loops. In some genera 

 (Psylla, Cicada, Nepa) the four vessels 

 open separately into the intestine ; in 

 others (Pediculus, Cixius, Capsus, 

 Pentatoma), either pair has but a 

 single duct. Frequently the common 

 ducts a^e swollen into vesicles (Velia, 

 Gerris, Lygaeus, Pentatoma, Cimex). 



The union of vessels both at their 

 distal and proximal ends is undoubt- 

 edly a secondary feature. In the em- 

 bryos of Cicada septe)ideci?n and 

 Zaitlia fluminea I fail to find any 

 union ; the vessels arise as four dis- 

 crete diverticula. 



It is more than probable that 4 is the 

 original number of Malpighian vessels 

 in the Rhynchota. The Coccidae and 

 Aphidae, the former with 2, the latter 

 without vessels, have lost one or both 

 pairs. That such is the case is shown 

 by the Coccid Orthezia catap/iracta^ 

 which still retains 2 pairs. 



* 1. c. p. 640. 



f Orthezia cataphracta, eine monographie. Zeitschr. 

 f. wiss, zool. bd. 45, 1S87. 



