Lot a 7 a 
change of structure and habit. The answer must be that, gene- 
rally speaking, some of the groups which are widely separated 
by dissimilarity of structure, possess the same kind of metamor- 
phosis, and that some groups which resemble each other more 
than others have not the same kind of changes. 
It is impossible to classify the groups by their kinds of changes 
of structure and habit without outraging the first principles of a 
natural classification. 
The next step in this inquiry is to decide whether all the mem- 
bers of any of the great groups are metamorphosed in the same 
manner, and whether there are any genera or species belonging 
to one group which are exceptional in their method of change, 
and which possess that common to the bulk of the insects of 
another group. 
The answers are as follow :— 
Allthe members of any great group are not subject to the 
same kind of change, but those of some very small families are ; 
and some genera undergo a metamorphosis totally unlike their 
closest allies in a group. 
There is a very good example of the difference in the mode of 
metamorphosis in some of the great groups, and of its evident 
jndepantenes of structural affinity or likeness to be gleaned by 
comparing the Orthoptera, the Coleoptera, and the Lepidoptera 
—the grasshopper, beetle, and butterfly tribes respectively. 
There is a greater resemblance in structure and general arrange- 
ment of parts between the Orthoptera and the Coleoptera than 
between the Coleoptera and the Lepidoptera ; yet the Coleoptera 
resemble the Lepidoptera in possessing complete metamorphoses, 
whilst those of the Orthoptera are incomplete or absent altogether. 
Again, many families of the great groups have genera whose 
species are influenced by very wide modifications of the same 
kind of change. Thus amongst a family of the Lepidoptera one 
kind passes through a perfect change like that already described. 
A closely-allied moth will pass through the change twice in the 
year; and in one the egg will remain unhatched through the 
winter; in another the pupa will Jast through the autumn, 
winter, and spring; in a third a perfect insect will hybernate 
through the water ; in a fourth a caterpillar will be born, will 
feed and increase in size, but will not turn to a pupa at once. 
It will hide up and hybernate for months, and will be metamor- 
phosed in the early spring. In a fifth a caterpillar will crawl 
from the egg in August, and will not eat; but it hides up and 
hybernates until the early summer, when it crawls forth and eats 
and passes through a perfect metamorphosis. All these modifi- 
cations, so irrespective of seasons, may be noticed in closely- 
allied genera. The lace-wing family, or the Neuroptera, are a 
yery natural group, and their separation from other forms, on 
account of the general dissimilarity of construction, is as perfect 
as any classification will permit. In this family all the kinds of 
metamorphosis are tobe noticed. Some genera, like the dragon- 
flies, undergo incomplete metamorphoses, and have active 
nymphs, which do not differ much from the larva ; whilst others, 
like the scorpion-flies and the caddis-flies, are subjected to 
changes as perfect as those of a butterfly or moth, although their 
structures are very diverse. 
Seeing, then, that insects which so closely resemble each other 
as to be placed as allies in every classification that follows the 
order and system of Nature have to undergo different kinds 
of change of structure and habit, it becomes necessary to admit 
that the original structures of a species assumed their form ac- 
cording to a law which did not regulate the metamorphoses. 
These have no relation with the origin of the species, and are 
independent of the anatomy of the individual. Like the struc- 
tures of the wings, the stages of the metamorphosis are acquired 
and superadded, It is credible enough that these wonderful and 
various changes are for the benefit of the creatures undergoing 
them ; and doubtless there has been in every instance a myste- 
rious relation between these and external physical conditions at 
some period or other. The metamorphoses are for the protec- 
tion and preservation of the species, and may be esteemed 
extraordinary aids in the struggle for existence. The fact of 
there being Insecta which do not undergo metamorphoses, 
but only the skin sheddings which are common to certain Arach- 
nida, Myriopoda, and Crustacea,—all the Articulata, is very im- 
portant in studying the philosophy of this knotty subject ; so 
also is the fact that the orders of Insecta which contain both 
these non-changing forms, and others which have a very incom- 
plete metamorphosis, are of vast geological age. Probably 
these Neuroptera and Orthoptera were the first insects—cer- 
tainly they were amongst the oldest. These considerations must 
ade 
TURE 
be associated with the method of development of wings—those : 
acquired organs which are, nevertheless, not present in some 
non-metamorp hosing Insecta. aa 
The most convenient hypothesis by which the origin of meta-— 
morphosis may be explained, and that which appears to be most 
consonant with facts, is to be comprehended under the follow- 
a 
ing heads :—1. The insecta havea great geological age. 2, The 
earliest did not undergo metamorphoses, but simply shed their 
skins. 3. The first forms were wingless Neuroptera or Orthop- 
tera. 4. That in order to meet the ng of changes in exter- 
nal physical conditions during the evolution of varieties of the 
original forms, the metamorphoses were acquired. 5. Incom- 
plete metamorphoses preceded the complete, 
were acquired independently of metamorphosis. 7. The kind 
of metamorphosis depended upon peculiarities in the external 
conditions, and its determination was defined by law. 
If the phenomena of metamorphosis and the growth of wings 
have been acquired, and were not implanted in the original 
species to follow at once and inevitably, there should happen, 
and there ought to happen—according to the analogy of nature 
—instances where the part or the whole of the acquisition is 
absent. 
The degraded and almost wingless vapourer moth, the wing- 
less Psyche, the wingless condition of the female of the winter 
moth, and the useless wings of Climatobid, must have arisen, — 
not by disuse, but by reversion to the ancestral condition. Why 
should the gall-flies that affect the roots of the oak have no wings, 
and those which make galls on the branches have them only in 
the male, whilst the makers of the corresponding structures on 
the leaf are perfect in their wings and metamorphosis? The idea 
of disuse will not apply ; and certainly the wingless would enjoy 
wings and make them useful. They are reversions to the ances- 
traltype. There is a little false wasp called Metilla: it belongs 
to a tribe eminently characterised by advanced instincts, and 
rapidity and power of variation of flight ; yet the female is wing- 
less, and low in its instincts. The wings would be useful to the 
insect, and the males of an Australian species certainly think so, 
for they carry their wingless ladies about with them under great 
difficulties. It is, like the others, an instance of reversion. On 
the other hand, the acquirement of the gift of imperfect meta- 
morphosis may have been followed by that of the complete kind, 
and then to that of the elaborate and apparently enigmatical — 
changes undergone by some parasites, may haye been super- 
added. - 
Habits and instinct which change contemporaneously with the — 
structural metamorphoses were doubtless acquired and are 
handed down, generation after generation, in obedience to the law 
of the descent and inheritance of useful gifts. Wonderful as the 
acquisition is of certain mental powers at certain periods in 
such humble things as insects, still it must be remembered that 
man inherits mental peculiarities, which become evident at 
different successive times of his life. A boy inherits mental 
peculiarities which characterised the youth of his parents, and 
others become evident in his adult age, which peculiarised his 
father or mother at the same period. How, is beyond the 
question and the fact is enough. 4 
Sometimes, by examining the instincts of a group of closely 
allied species of insects, and by noticing and comparing slight ; 
differences .in their habits and metamorphoses, a hint may be 
obtained how some very recondite peculiarity may have been 
acquired and been transmitted, provided it were beneficial to the 
creature. The most interesting instincts of the Odynerus which 
were mentioned at the commencement of this lecture, were the 
forming a tubular antechamber and provisioning the chambers 
with stung grubs for an offspring which it neversaw. A con- 
siderable group of mining false wasps make or excayate 
chambers to lay their eggs in, and they, one and all, are in con- — 
stant terror lest some interloper or parasite should enter their 
underground workings, during their absence in search of food for 
the future offspring. On arriving with the stung larva at the 
mouth of their hole, which is closed up carefully by some before 
flying off, they enter and run into the chambers in a great state of 
excitement to see that the nursery is not taken possession of by 
an intruder who intends to stop. So impressed is this instinct 
upon them that, if the prey which is left outside during the rapid 
inspection be removed a little way off, when it is replaced by the 
insect the process of examination is repeated, and the insect will 
do this over and over again, senselessly it is true, but in obedience 
to an inherited and almost automatic impulse. 
There is no doubt that a great number of futile egg layings and — 
6. Organs of flight 
v 
