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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.) 



Laineere 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. 



\Vheeler 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 



A 



ef. 



B 



-Ibr 



Ilim- 



FIG. 529. Primitive band of Bombi/.r mori, -bowing the temporary legs on abdominal seg- 

 ments '2-11 : .1, early staire. in which the abdominal leys <i/--n/'" appear. ' />', later staire. hen they 

 an- M-I \ lain! ami all except ni s -ul e ' and al w are about to disappear. t\ the persistent abdominal 

 legs <//''' ill 1 '' and ill 1 " ; .v/ 2 , .s7 ; ', the 2d and 3d pair of stigmata ; x<jl. silk duct. After Tichomiroff. 



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

 both Bombyx mori and Gastropacha quercifnlni (except those of the 

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

 ;ip|)cii(l;i^cs, has suggested tliat the prop or prolegs of caterpillars 

 ;iinl sa. \v-fly larva 1 , 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 



