282 Mr. T. D. A. Cockerell on new Bees 



it a necessity (perhaps for protection against injiuy, as Kor- 

 schelt and Heicler suggest (4)) for the embryo to be covered 

 over at an early stage in its development. The physico- 

 chemical forces which led to the origin of this adaptive 

 covering cannot be defined at present, but the result was that 

 as soon as the first rudiment of the embryo, the germ-disk, 

 became established a portion of it folded over the rest and 

 became the amnion. This would occur most readily in forms 

 which, like some Orthoptera and the termite, begin in a small 

 germ-disk. When forms arose among the higher insects as 

 adaptations to special conditions of life the early completion 

 of tins process became less important, and in a few extreme 

 cases this led to the degeneration and disappearance of the 

 membranes. 



(1) Brandt, A. — ' Beitrage ziu- Entwicklungsgescliichte der Libellu- 



liden und Ilemipteren.' 1869. 



(2) Britce, a. T. — ' Embryology of Insects and Arachnids.' 1887. 



(3) Gkaber, V. — ' Vergleiehende Studien am Keimstreif der In- 



secten.' 1890. 



(4) KoRSCHELT und Heider. — ' Lehrbuch der vergleicbenden Ent- 



Tvicklunofsgescbichte,' 1S90. 



(5) McMuRRicH, J. P. — ' Embryology of Isopod Crustacea.' 1895. 



(6) Patten, Wm. — ' The Development of Phryganids.' 1884. 



(7) ViALLAXES, H. — ' Sur quelques points de I'histoire du d4veloppe- 



ment Embryonnaire de la Mante religieuse.' 1889-90. 



(8) Wheeler, W. M. — ' The Embryology of Blatta gen-manica and 



JDoryphora decent I ineata.' 1890. 



(9) Wheeler, W. M. — 'Contributions to Insect Embryology.' 



1893. 

 (10) Heymons. — 'Development of Orthoptera and Dermaptera.' 1895, 

 (Abstracted in Journ Roy. Micr. Soc. 1894.) 



XLiy . — Contributions from the Xeio Mexico Biological Station. 

 — I. Descrijytions of new Bees collected by Prof. G. H. T. 

 Tovmsend in the State of Vera Cruz. By T. D. A. 

 COCKERELL. 



When Prof. Townsend lately went for a collecting trip in 

 Mexico 1 pointed out to him that, although many bees had 

 been described from that country, we were totally ignorant of 

 their habits, the flowers they visited, and so forth. Accord- 

 ingly he collected a large series of specimens, noting in every 

 case the exact locality and date, and preserving specimens of 

 the flowers on which the bees were caught. The collection 

 thus brought together is of great interest, not only for the 



