12 



THE ANATOMY OF THE HONEY BEE. 



tion of a form with complex organs from the simple protoplasmic 

 mass of the egg. The part of development that takes place in the 

 eggshell is known as embryonic development; that which takes place 

 subsequent to hatching is known as postemhryonic development. In 

 insects there are often two stages in the postemhryonic development, 

 an active one called the larval stage and an inactive one called the 

 pupal stage. During the first of these the young insect is termed a 

 larva; during the second, a pupa. When there is no resting stage the 

 immature creature is often called a nymph. The final and fully de- 

 veloped form is an adult, or imago. 



Since this paper is to deal only with the anatomy of the adult, the 

 attractive fields of embryonic and postemhryonic development must 

 be passed over, except for a few statements on 

 fundamental embryonic structure, a knowledge 

 of which is necessary to a proper understanding 

 of the adult anatomy. 



When the embryo, in its course of development, 

 first takes on a form suggestive of the definitive 

 insect, it consists of a series of segments called 

 metameres, or somites, and shows no differentia- 

 tion into head, thoracic, and abdominal regions. 

 Typically, each segment but the first is provided 

 with a pair of latero-ventral appendages, hav- 

 ing the form of small rounded protuberances. 

 These appendages are of different sizes and take 

 on different shapes in different parts of the 

 body, for some of them are destined to form the 

 antenn£E, some the mouth parts, others the legs 

 and perhaps the cerci, while the rest of them 

 remain very small and finally disappear. What 

 we know of the embryology of insects is based 

 on the observations of a number of men who 

 have worked mostly on the development of dif- 

 ferent species. Their observations are not all 

 alike, but this is probably due in large part to the fact that the 

 embryos of different insects are not all alike. Embryos have a very 

 provoking habit of skipping over or omitting little and yet im- 

 portant things m their development, but fortunately they do not 

 all omit the same things. Therefore, by putting together all the 

 reliable information we possess, we can make up an ideal embryo 

 which would be typical of all insects. Such a generalized embryo is 

 represented diagrammatically by figure 2. 



The first six or seven metameres very early begin to unite with 

 one another and continue to fuse until their borders are lost. These 

 consolidated embryonic segments form the head of the adult insect. 



Fig, 



An- 



2. — Diagram of a 

 generaUzed insect em- 

 bryo, showing the seg- 

 mentation of the head, 

 thoracic, and abdom- 

 inal regions, and the 

 segmental appendages. 



