THE DEVELOPMENT OF PATTERNS IN THE
INTEGUMENT OF INSECTS
MICHAEL LOCKE
Developmental Biology Center, Western Reserve University, Cleveland, Ohio
I. Introduction
33
A. The Structure of the Integument—Types of Cuticle
34
B. Pathways of Differentiation Open to a Postembryonic Epidermal Cell .
40
C. Humoral Control
43
II. Problems in Pattern Formation
43
A. The Formation of Surface Patterns
44
B. The Gradient Organization of Segmentally Repeating Patterns .
.
57
C. Three-Dimensional Patterns Resulting from Cycles of Activity in Time
82
References
87
I. Introduction
The success of chemical embryology in formulating developmental
problems in terms of specific protein synthesis, even if the mechanism by
which genes control processes is still incompletely understood, has tended
to draw attention away from studies on the determination of patterns in
space. An outstanding problem is the elucidation of the mechanisms by
which these chemical changes, patterns in time, are translated into
morphological changes, patterns in space. The problem is a compound
one which can be attacked at several different levels from the molecular
to the organismal. At each level the problem is twofold: (1) the origin
of the ordered structure, and (2) its orientation and position relative to
other ordered structures or to part or the whole of an organism. Several
features of the integument of insects lend themselves to studies of these
problems. On the one hand, we have the techniques and concepts derived
from Drosophila genetics and the large number of cuticular mutations.
On the other hand, we have in the integument a single sheet of epidermal
cells which record their previous synthetic activities in the layers of cuticle
which they secrete. Within the epidermis, some cells are destined for
fates different from their neighbors, and reflect their local differentiation
in the variety of surface structures (bristles, scales, dermal glands, surface patterns). Although all the developmental problems posed in an
embryo have their parallel in the formation of the integument and its
33
INTEGUMENT OF INSECTS
MICHAEL LOCKE
Developmental Biology Center, Western Reserve University, Cleveland, Ohio
I. Introduction
33
A. The Structure of the Integument—Types of Cuticle
34
B. Pathways of Differentiation Open to a Postembryonic Epidermal Cell .
40
C. Humoral Control
43
II. Problems in Pattern Formation
43
A. The Formation of Surface Patterns
44
B. The Gradient Organization of Segmentally Repeating Patterns .
.
57
C. Three-Dimensional Patterns Resulting from Cycles of Activity in Time
82
References
87
I. Introduction
The success of chemical embryology in formulating developmental
problems in terms of specific protein synthesis, even if the mechanism by
which genes control processes is still incompletely understood, has tended
to draw attention away from studies on the determination of patterns in
space. An outstanding problem is the elucidation of the mechanisms by
which these chemical changes, patterns in time, are translated into
morphological changes, patterns in space. The problem is a compound
one which can be attacked at several different levels from the molecular
to the organismal. At each level the problem is twofold: (1) the origin
of the ordered structure, and (2) its orientation and position relative to
other ordered structures or to part or the whole of an organism. Several
features of the integument of insects lend themselves to studies of these
problems. On the one hand, we have the techniques and concepts derived
from Drosophila genetics and the large number of cuticular mutations.
On the other hand, we have in the integument a single sheet of epidermal
cells which record their previous synthetic activities in the layers of cuticle
which they secrete. Within the epidermis, some cells are destined for
fates different from their neighbors, and reflect their local differentiation
in the variety of surface structures (bristles, scales, dermal glands, surface patterns). Although all the developmental problems posed in an
embryo have their parallel in the formation of the integument and its
33