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TEXT-BOOK OF ENTOMOLOGY 



(Acilius)." They attain their greatest size during the revolution of 

 the embryo, and they are " mere rudiments of what were probably in 

 remote ages much larger and more complex organs." (Wheeler.) 



Lameere has observed that in Phyllodromia the first pair of abdominal appen- 

 dages, after becoming of considerable size, undergo an enlargement at their free 

 end, become detached, and fall into the amnion. 



Wheeler also calls attention to the hoinology of these pleuropodia with the 1st 

 abdominal appendages of Campodea, shown by Haase to be originally glandular, 

 but with at present a respiratory function. In the embryos of later, higher 

 orders of insects, these appendages are in size and shape similar to those of the 

 succeeding segments. (See also p. 164.) 



Are the abdominal legs of larval Lepidoptera and phytophagous Hymen- 

 optera true limbs ? The presence of these abdominal legs in the 



,11m 



FIG. 529. Primitive band of Bombyx inori, showing the temporary legs on abdominal seg- 

 ments 2-11 : A, early stage, in which the abdominal legs al--al l(i appear. , later stage, when they 

 are very faint and all except al 3 -af K and al w are about to disappear. (?, the persistent abdominal 

 legs aP-al 6 and afl ; st 1 , < 9 , the 2d and 3d pair of stigmata ; sgl. silk duct. After Tichomirott'. 



embryos of Sphinx (Kowalevsky), ofBombyxmori (Tichomiroff), and 

 both Bombyx mori and Gastropacha quercifolia (except those of the 

 first segment), as well as in Hylotoma, which has 11 pairs of such 

 appendages, has suggested that the prop or prolegs of caterpillars 

 and saw-fly larvae are survivals of these outgrowths, and not second- 

 ary, adaptive structures. Opinions on this point vary. Balfour, and 

 also, more recently, Cholodkowsky, hold that the prolegs are sur-~ 

 vivals of the embryonic appendages. Graber cautiously, after a 



