56 
Silvestri und Dewitz, zwingen uns zu einer bedeutenden Anderung 
der allgemeinen Anschauung über die Mal pighischen Gefäße als aus- 
schlieBliche Excretionsdriisen. Im hier beschriebenen Falle haben wir 
es vielleicht mit einer entgegengesetzten Funktion zu tun, d. h. mit 
einer Secretionsfunktion. Die in den Malpighischen Gefäßen ge- 
bildeten Stoffe häufen sich während dem Larvenleben in ihnen an, um 
schließlich nicht in Form untauglicher Produkte abgegeben, sondern 
gänzlich zum Bau des die Phytonomus-Larve schützenden Kokons 
verbraucht zu werden. 
2. The Ground Plan of a Typical Thoracic Segment in Winged Insects. 
G. C. Crampton, Ph. D.1. 
(With 1 figure.) 
eingeg. 8. Januar 1914. 
The “ground plan” of a wing-bearing thoracic segment shown in the | 
accompanying figure represents an hypothetical composite type, to which 
the thoracic segments of any insect can be referred as a basis of com- 
parison, rather than an attempted reconstruction of the original con- 
dition of the thoracic sclerites in the ancestors of winged insects. Most 
of the primitive features, however, are included in the figure, and to 
these have been added conditions found in the more specialized insects. 
As here represented, the typical thoracic segment is not compound, or 
composed of subsegments, since the writer is convinced that all of the 
“compound-segment” theories are unfounded. The three thoracic seg- 
ments of the adult insect represent the three thoracic segments of the 
embryo — and no more. 
Contrary to the prevalent conception of the origin of the thoracic 
sclerites, these were not formed by the breaking up of solidly chitinized 
rings (forming the body wall of the segments) as Woodworth, 1906, 
maintains; but originated as isolated plates, formed by the stronger 
deposition of chitin and pigment in the softer body wall, due to the 
stimulus of muscular tension and mechanical stimuli. This is well shown 
in larval insects (e. g. Carabidae) and in the lower forms such as Japyz, 
Embia, and particularly the Myrientomata, figures of which were very 
kindly shown me by Dr. Prell, who is about to publish a paper dealing 
with the thoracic sclerites of these interesting insects. In the higher 
insects, certain of these plates unite to form continuously chitinized 
areas which are subsequently subdivided by the formation of secondary 
sutures (i. e. those not originally present) which tend to mask the origi- 
nal condition. 
1 Contribution from the entomological laboratory of the Massachusetts Agri- 
cultural College, Amherst, Mass. 
