ORIGIN OF A METAMORPHOSIS IN INSECTS. 
299 
larvae. Brauer’s figures show a pair of abdominal, two-jointed feet to 
each of the nine abdominal segments, while just as in Lepidopterous 
larvae and in that of Panorpa there is a pair of prothoracic spiracles, 
none on the mesothoracic or metathoracic segments, and there are nine 
pairs of abdominal spiracles according to Brauer’s figure, or one more 
pair than in Lepidopterous larvae. 
The fact that there are in the larval Panorpid® collectively a pair of feet 
to each abdominal segment (the terminal segment in Panorpa bearing 
what are evidently homologues of the anal proplegs of caterpillars) is 
of much significance when we bear in mind that while no caterpillars are 
known to have more than five pairs of abdominal or proplegs, some of 
the segments bearing none, yet the embryos, as shown by Kowalevsky, 
have temporary embryonic indications of legs, a pair to each segment 
(uromere) ; it is a significant fact that the cruciform larva; of the Panor- 
pid® actually have two-jointed legs to each abdominal segment, the 
penultimate segment in Bittacus bearing such legs, and the terminal seg- 
ment bearing leg-like processes in Panorpa. The origin of the Lepi- 
doptera from the same stem-form as the Panorpid® thus seems a rea- 
sonable hypothesis. 
In the metamorphosis of Mantispa, as Brauer has shown, there is a 
hypermetamorphosis, i. e., two larval stages. The first stage is Campodea- 
form ; but the second is sub-eruciform. The transformations of Mantispa 
appear to give us the key to the mode in which a metamorphosis was 
brought about. The larva, born a Campodea-like form, active, with large, 
long, four-jointed feet, living a sedentary life in the egg-sac of a spider, be- 
fore the first molt loses the use of its feet, while the antenu® are partly 
aborted. The fully grown larva is round-bodied, with small, caterpillar- 
like feet and a small, round head. Its external appendages retrograding 
and retarded, acceleration of growth goes on within, and thus the pupal 
form is perfected while the larva is full-fed and quiescent; hence as a 
result the pupal stage became a quiescent one, and by inheritance it grad- 
ually became a permanent habit characteristic of Neuroptera, all of which 
have a complete metamorphosis, and hence inherited by all the orders of 
metabolic insects which probably originated from Neuroptera-like forms, 
and the imago represents a highly accelerated stage. 
When we consider the imagos or adult Neuroptera : the small, collar- 
like prothorax, the spherical, concentrated thorax as a whole, and the 
cylindrical abdomen, are features which give them a comparatively spe- 
cialized and modern aspect. Without doubt the Neuropterous labium 
(Plate LIII) is a secondary product compared with that of the Orthoptera 
or the Platyptera, where it is deeply cleft (Plate XXVII.) It will be re- 
membered that in the embryo of all insects the labium or second maxill® 
originates like the first pair. 
Origin of the Goleoptera . — Although the beetles are a remarkably 
homogeneous and well circumscribed order, there are certain larval 
forms and life-histories which point out with a tolerable degree of cer- 
