1894.) Entomology. 191 
Pupal Development and Color in Imago.—Discussing the 
recent experiments of Merrifield in which lepidopterous pupe were 
submitted to various temperatures and the results on the imagoes noted, 
Mr. J. W: Tutt briefly recapitulates’ the well-known facts of histolysis 
and continues thus: “If we apply the simplest elementary laws relat- 
ing to vital force to the pupa, we shall find that the following facts 
hold good :—(1). The pupa when first formed has a certain amount 
ofinherent vital force by means of which both the processes of histoly- 
sisand rehabilitation are carried on in it. (2). That pupa which has 
the nearest approach to the normal amount of vital force will undergo 
the most perfect histolysis and rehabilitation, and will produce an 
imago most nearly conforming to what is known as the normal type, 
that is the type produced under the most healthy and satisfactory con- 
ditions. Conversely that pupa whose amount of vital force is farthest 
removed from the normal (whether in excess or in defect) is one in 
which histolysis and rehabilitation will be least perfect, and the imago 
produced will be the farthest removed from the normal type. (3). 
That individual which has been best fed and which had enjoyed the 
most perfect health in the larval stage, will enter pupal life under 
the most satisfactory conditions and will (the pupal conditions being 
equally satisfactory) emerge therefrom as the best specialized product, 
whilst the converse to this must also be true. 
“The second point also deals with an elementary principle. The 
vital force in the pupa is converted into energy ; the energy at the dis- 
posal of the pupa is most probably directed first to the building up of 
the vital reproductive organs, and afterward to the secondary organs 
or tissues or such as are not necessary to life. Therefore an excess of 
energy in a pupa will be expended as a rule on secondary structures 
rather than on vital ones, and we find that a weak or diseased pupa 
fails first in regard to non-vital tissues, such as pigment, scales, wing- 
membrane, etc. 
“The females of insects, as compared with the males require an 
excess of energy for those structures necessary to the reproduction of 
the species ; they, therefore, have a smaller surplus to devote to the for- 
Mation of the non-vital tissues, and as we well know frequently fail 
very markedly in their development of these. : 
“ We are now in a position to understand that as a general rule pig- 
ment, scales, etc., are produced in proportion to the amount of material 
and energy available for the purpose, 
"The Entomologist’s Record, 1V, 312. 
