November 1893. J 



PS TC HE. 



54 4 



gleiche harngefasse vorfand." It is 

 perhaps worthy of note that this pen- 

 tanephric condition obtains in Diptera 

 which are by common consent among the 

 most ancient and primitive of the order. 



The foregoing remarks may be sum- 

 marized as follows : — 



r. It is very probable that the so- 

 called Malpighian vessels of Crustacea 

 and Arachnida are not the homologues 

 of the vasa Malpighi oi the Eutracheata 

 (Insects and Myriopods). 



2. The Malpighian vessels of the 

 Eutracheata arise as paired diverticula 

 of the hind-gut and are, therefore, 

 ectodermal. 



3. In no insect embryo are more than 

 6 vessels known to occur ; although 

 frequently only 4 are developed. 



4. The number 6 occurs either dur- 

 ing embryonic or post-embryonic life in 

 members of the following groups : Ap- 

 terygota, Orthoptera, Corrodentia, Neu- 

 i"optera, Panorpata, Trichoptera, Cole- 

 optera, Lepidoptera and Hymenoptera. 



5. The number 4 seems to be typical 

 for the Corrodentia. Thysanoptera, 



Aphaniptera, Rhynchota, Diptera and 

 Hymenoptera. 



6. The embryonic number in Derm- 

 aptera, Ephemeridea, Plecoptera and 

 Odonata has not been ascertained, but 

 will probably be found to be either 4 or 6. 



7. There is evidence that in at least 

 one case (Melolontha) the tetranephric 

 is ontogenetically derived from the 

 hexanephric condition by the suppres- 

 sion of one pair of tubules. 



S. It is probable that the insects 

 which never develop more than 4 Mal- 

 pighian vessels have lost a pair during 

 their phylogeny. 



9. The post-embryonic increase in the 

 number of Malpighian vessels in some 

 orders (Orthoptera, Odonata, Hymen- 

 optera) is secondary and has apparently 

 arisen to supply a demand for greater 

 excreting surface.* 



* There is a curious analogy between the excretory- 

 organs of these insects and the mesonephros of some 

 vertebrates, where a second, third, etc., generation of 

 tubules is added to the primitive metameric series. 

 When the embryonic number of Malpighian vessels 

 persists in insects, the demand for greater excreting 

 surface is supplied by a lengthening of the individual 

 vessels. 



NOTE ON A SCUTELLERID ON NATIVE TOBACCO IN ARIZONA. 



BY C. H. TYLER TOWNSEND, KINGSTON, JAMAICA. 



At Cedar Ranch, Arizona, which is and is on the edge of the somewhat 



the half-way station on the stage route mountainous country which lies to the 



from Flagstaff to the Grand Canon, I south of it. a more or less level plateau 



found on July 6, 1892, a scutellerid in extending to the north between it and 



numbers on a species of native tobacco, the canon. The native tobacco upon 



Nicotiana sp. probably attenuata . which the insects were found grew in 



This locality is also called Hull Spring, patches about the spring, which is 



