of the Oil Beetle, Meloé, and of the Strepsiptera. 347 
the summer or autumn, and probably always subsequent to the change of the 
bee- or wasp-larva. This I have found most certainly the case in Ichneumon 
Atropos, in Sphinx Ligustri, which remains in its original position, but never 
changes to a nymph until long after the caterpillar in which it lives has be- 
come a chrysalis. The changes of the Stylops follow those of the insect on 
which it is a parasite in quick succession. The bee has often completed its 
changes in the autumn, but, as naturalists are aware, does not then leave its 
cell. It remains in it during the winter in a state of hybernation, and comes 
forth in the spring. The Stylops, like the bee, also appears to complete its 
changes in the autumn, as is proved by the fact related by Mr. Pickering *, 
that a living male Stylops issued forth from the body of an Andrena tibialis, 
which he dug out of its cell alive at the end of December. That the apodal 
females also undergo their slight change, and are prepared to emerge between 
the segment of the bee at about the same period as the males, has been proved 
by Dr. Siebold. 
COMPARISON OF THE SEXES OF SryLops, 
A comparison of the sexes of Strepsiptera exhibits perhaps one of the most 
striking contrasts we are acquainted with in nature. Every structure of the 
body in the male which has relation with the external world exists in a con- 
dition the very opposite of that of the female. In the one sex the organs of 
sense and locomotion are developed to their utmost extent; in the other their 
development is arrested at its very commencement. Yet both sexes exist 
under precisely similar conditions of structure and relation at the moment of 
their liberation from the incubatory organ of their parent, and during their 
larva period of nutrition. When this period is completed, the formative ener- 
gies or forces of the primary constituents of the body in the one are con- 
centred in the production of ova,—of thousands of similar combinations of 
matter, each constituted to result in the formation of an organized body, iden- 
tical with that in which it has itself been produced. In the other sex the 
powers of life are not exhausted simply in the production of new combinations, 
tut mainly are employed in the unfolding of those which belong to the body 
itself, and which are to bring it into immediate communication with the ex- 
ternal world as an independent being. The sole design of the existence of the 
* Trans. Ent. Soc. vol. i, part 3, P. 164 et seq. 
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