414 
ZOOLOGICAL LITERATURE. 
Packard detected tlie remains of a thin pellicle upon the extre- 
mities, from which he regards these individuals as representing 
a subimago state analogous to that of the Ephemerid(e ; and 
hence he considers that, including the emergence from the egg, 
the Bomhi may be considered to undergo a series of at least 
ten moultings of the skin.^^ The evidence of a subimago state 
appears, however, to be very imperfect. 
The author next enters upon a consideration of the number of 
arthromeres composing the head in insects. The pleural region 
is the limb-bearing region of the body ; and the development of 
the three regions of the arthromere [tergitej sternite, ^.ndipleurites) 
will depend upon the development of the appendages. Thus in 
the abdomen the tergites and sternites are most developed, in 
the thorax the pleurites come into prominence, and in the 
head the larger portion is pleural, and the tergal and especially 
the sternal parts are either very slightly developed or wholly 
obsolescent.^^ The consideration of the number of pairs of ap- 
pendages attached to the head leads the author to regard that 
part as theoretieally composed of seven arthromeres. The body 
of an insect thus consists of 20 segments, of which 7 belong to 
the head, 3 to the thorax, and 10 to the abdomen. The Myria- 
pods, according to Packard, form an order of the class Insecta. 
The author refers to his proposed elassifieation of inseets in two 
series, — one eommeneing with the Neuroptera, and passing 
through the Orthoptera and Hemiptera, to culminate in the 
Coleoptera-y the other, which ranks higher as a whole, eommences 
with the Diptera and terminates with the Hymenoptera, which 
thus occupy the highest place in the class of insects. Packard 
refers to various structural indications of this superiority in the 
Hymenoptera j of which he regards as the most striking single 
charaeter the transfer of the first abdominal segment forward to 
the thoracie region. The study of ‘^MegradationaP’ and wing- 
less forms in the various orders of inseets leads the author to the 
same conclusion, as does also the consideration of the geological 
range in time of the known forms of this class. 
Packard, A. S. Revision of the Fossorial Hymenoptera of North 
America. I. Crabronidoi and Nyssonidce, Proc. Ent. Soc. 
Philad. vol. vi. pp. 39-115 ; June 1866. 
In this paper. Packard commences an elaborate revision of the 
North- American Fossorial Hymenoptera, in which the whole of 
the species are tabulated, but, as a general rule, only the new ones 
characterized at greater length. In his opening remarks the 
author has some judicious observations on the modern system of 
excessive subdivision, especially on the praetice of giving family 
or tribal names to minor collections of genera connected by 
characters of very slight importance,^^ and on the inconvenience 
of burdening the nomenclature of scienee with an immense 
