THE EMBRYOLOGY OF THE HONEY BEE 101 



darker ones ; the last two segments, the twelfth and thirteenth, are 

 however not yet clearly separated. On the ventral side the inter- 

 segmental light zones broaden out and unite along the mid-line, 

 so that here the segments are represented by dark processes 

 stretching out from the sides toward the mid-line. These darker 

 areas represent the mesodermal somites. 



The germ band is of almost uniform width from the mandibu- 

 lar segment to the twelfth trunk segment, widening only a trifle at 

 the fourth and fifth trunk segments. On the three segments next 

 following the head, on the ventral side are seen the faint outlines 

 of three pairs of larger appendages, which are the rudiments of 

 the thoracic legs (iL, 2L, jL). 



Contemporaneous with the appearance of the rudiments of the 

 mouth parts and legs is the appearance of the invaginations which 

 form the silk glands and tracheae. The rudiments of the silk 

 glands (SlkGl) are plainly seen as a pair of small pale apertures 

 transversely elongated, situated just caudad of the bases of the 

 rudiments of the second maxillae. The common rudiments of 

 the spiracles and tracheal system appear as a linear series of ir- 

 regular apertures on each side of the germ band, a pair being evi- 

 dent on the second, third, fourth, fifth and sixth trunk segments, 

 the first pair being the largest and most distinct, and the last the 

 smallest and faintest. Since the definitive number, ten pairs, is 

 found in the stage next following, it is apparent that the tracheal 

 rudiments at Stage VIII are just making their appearance and 

 also that they develop successively caudad. 



Stage IX, 52-54 hours (Fig. IX). At this stage the germ band 

 has not altered in its general appearance or proportions but all of 

 the rudiments present in- the preceding stage are more sharply 

 defined. Those of the mandibles and maxillae are now well de- 

 fined ovoid swellings, distinctly marked off from one another 

 and plainly raised above the general level of the germ band. 

 The premandibular appendages or second antennae are at this 

 stage best developed, being well defined rounded eminences situat- 

 ed just in front of the mandibles and a trifle nearer the mid-line. 

 A line connecting them would pass just below the stomodaeal in- 

 vagination. The rudiments of the first pair of thoracic legs are 

 more clearly marked off than before, but those of the second and 

 third pairs are ill-defined, their position being still marked only 



