gniomolagists 
ae “ong 
JOURNAL oF VARIATION. 
Vor, Xalie® Not 6: JunE Ist, 1900. 
The Relationship between the Larval and Imaginal Legs of 
Lepidoptera (with Plate). 
By T. A. CHAPMAN, M.D., F.Z.8., F.E.S. 
The Orthoptera, which we may assume, for our present purpose, to 
have been the primitive insects, leave the egg with their legs, as far as 
number of articulations is concerned, except perchance as to tarsal 
joints, precisely of the same structure as they present in the mature 
insect. In Lepidoptera this is not so, the larve have legs consisting 
of a basal piece, of three chitinous joints, and a terminal claw, with 
palpal appendages ; whilst the imago has eight articulated pieces in 
the leg besides the claws and appendages. It even happens in some 
species that the larve are without legs. This is a common condition 
in Coleoptera, Diptera, and Hymenoptera. 
On examining the leg-structure of a typical imago of almost any 
order, we find the tarsus consisting of various articulated segments up 
to five, of the two long segments, the femur and tibia, and of two basal 
segments, the coxa and trochanter. If we take a Micropteryx or Frio- 
crania we find precisely these structures, but if we select any of the 
higher lepidoptera, say Porthetria dispar, we find this structure present 
only in the prothoracic legs. In the others the first or coxal piece is 
soldered to the thorax, and though we may think we see its outlines, 
it is doubtful whether that is so, so that the statement with which I 
began, that there are eight articulated segments to the limb, is correct 
as to these, but the prothoracic leg has nine. 
It is to be remarked here that the larve of Trichoptera have both 
coxa and trochanter well-developed, contrasting strongly with their 
absence in lepidopterous larvee, and making one of the strongest points 
in their claim to be a separate order from Lepidoptera. Nevertheless 
the remaining three joints in the larval trichopterous lee, are remark- 
ably like the three joints in the lepidopterous larva, and since in the 
trichopterous larva these are unquestionably the femur and tibia and 
the tarsus reduced to one joint, the close alliance of the two groups 
justifies us in making the three joints of the larval lee in Lepidoptera 
the femur, tibia, and tarsus. 
Assuming the descent of the Lepidoptera from some Neuropteron, 
and ultimately from some Orthopteron with fully developed larval 
appendages, we are given two theories of how the lepidopterous larva 
became so worm-like and with such degenerate appendages. One, 
which I fancy is now obsolete, is that the lepidopterous larva repre- 
