250 THE EMBRYOLOGY OF THE HONEY BEE 



eleven days, or 264 hours, while that of the bee is only seventy-six 

 hours. The only way in which the length of time consumed by each 

 period in the two insects can be compared is by expressing it as a 

 fraction of the time required for total development. This is most 

 conveniently expressed by decimals. The time of each period 

 except the first, is calculated from the close of the preceding 

 period. The result is shown in the following table : 



Period I II III 



Hydrophilus 0.272 0.091 0.636 



Apis O-579 0.078 0.342 



The discrepancy between these figures is striking. In Hydro- 

 philus slightly over one-fourth of the time required for total devel- 

 opment is taken up by the first period ; in the bee over one-half is 

 consumed. Period II consumes relatively but a trifle more time 

 in Hydrophilus than in the bee, while period III consumes nearly 

 twice as much. If the time required for the formation of the 

 blastoderm be similarly compared, the result is expressed by the 

 fractions 0.166 for Hydrophilus, and 0.39 for Apis. Expressed 

 in general terms, it may be said that as compared with Hydro- 

 philus, the earlier development of the bee is greatly delayed or 

 conversely, that the later development is greatly accelerated. So 

 little is known of the vital forces underlying development that 

 the reason for these differences can only be surmised. It seems 

 not improbable however that one factor is the relatively slight 

 degree of differentiation of the bee larva, as compared with that 

 of Hydrophilus. The larva of the latter insect is fitted to lead an 

 active existence, finding, catching and killing its prey, and at the 

 same time avoiding its enemies. It is therefore well equipped 

 with functional organs of locomotion and perception together with 

 a well developed central nervous system, most of which in the bee 

 larva are present only as rudiments, and do not become functional 

 to any considerable degree until after metamorphosis. 



