OCT 30 1900 
No. 5.— The Development of the Mouth-Parts of Anurida 
maritima Guer4 By Justus Watson FoLsom. 
CONTENTS. 
PAGE PAGE 
Introduction ... . . . . . 87|Linguaand Superlingue .... 110 
WeTHOUSH mE een cs oe ts er) So Maxiller 5 08a) cet ber oe ie ALD 
General Description of Egg . . . 89|Labium .........~. 126 
Rane Singers 2 ¢ o 6 o a GWHISOIIl. 696 g56 G56 6 Ga o WS 
Procephalic Lobes . . . , . . Q91}]Tentorium.. . 6 6 9 TEY 
Labrum and Clypeus . . . . . 93} Segmentation of the Head Eee Uy 
Antenne . o @ of olism, 6 oe 6 62a og o o Tels 
Dremandibular’ Appendages s o o CbBiiieareNNy 6 of 6 5 6 o 6 co I 
Mandibles . . . ve 02) |) Explanationiof Plates sncmsen san elon 
Introduction, 
Our present ideas of homology in the details of insect mouth-parts 
rest almost exclusively upon anatomical data, and need careful revision 
in the light of embryological facts. 
Too many entomologists have speculated upon the subject in complete 
disregard of evidence from ontogeny or phylogeny. Embryologists, on 
the other hand, have greatly neglected the mouth-parts. 
It seems almost superfluous to insist that highly specialized organs 
can be but imperfectly understood unless studied in egg and larva as 
well as imago ; that generalized types illuminate specialized forms ; and 
that equivalent groups are linked together through their more general- 
ized members ; yet too often these accepted principles are not applied. 
The objects ‘of the present paper are two: first, to supplement my pre- 
vious account (Folsom, ’99) of the anatomy and functions of the mouth- 
parts of a representative Collembolan ; second, to discuss the morphology 
of mandibulate mouth-parts of insects and their nearest allies upon 
anatomical and embryological evidence derived from the most primitive 
insects, the Apterygota. 
1 Contributions from the Zodlogical Laboratory of the Museum of Comparative 
Zoviogy at Harvard College, E. L. Mark, Director, No. 114. 
VOL. xxxvi.— No. 5 
