THE INTERNAL STRUCTURE OF ANTS. 



37 



The Glandular System. Glands are well-developed in ants, and, 

 owing to their importance in the ethological relations of these insects, 

 deserve particular notice. They have been studied by Meckel (1846), 

 Leydig ( 1859), Meinert (1860), Forel (1874, 1878), Lubbock (1882), 

 Nassonow ( 1889) and Janet ( 1894, 1898). The following groups may 

 be distinguished: 



1. Integumentary glands, arising in the embryo, larva or pupa as 

 invaginations of the ectodermal cell-layer ( hypodermis ), and including 

 the antennary, mandibular, maxillary, labial and metasternal glands, 

 those of the' sixth abdominal (third or fourth gastric) segment, and of 

 the fore metatarsus. Here, too, may be included the unicellular glands 

 connected with the olfactory and tactile organs, to be considered in the 

 next chapter. All the integumentary glands are present in the male as 

 well as in the worker and female ant. 



2. Reproductive glands, including the penial glands of the male, and 

 in the worker and female the homologous glands of the sting-sheath, 

 belonging to the ninth abdominal (sixth or seventh gastric) segment; 

 the poison, accessory and repug- 



natorial, or anal glands of the 

 worker and female, and the 

 glands of the seminal vesicle of 

 the male. 



3. Glands of the alimentary 

 canal. These comprise the post- 

 pharyngeal, ventricular and rec- 

 tal glands and the Malpighian 

 vessels. 



4. Glands of the circulatory 

 system, including the oenocytes, 

 pericardial cells and adipocytes, 

 or fat body. These, unlike the 

 three other categories of glands, 

 are ductless. 



The glands of the alimentary 

 tract have been briefly described, 

 and those of the circulatory and 

 reproductive systems will be 

 taken up later, so that here only 

 the integumentary glands will be 

 considered. The antennary glands consist of a few isolated cells with 

 slender ducts opening on a small area in a depression at the base of 

 each antenna. The mandibular glands (Fig. 17, ing) are well-de- 



..ol 



FIG. 17. Frontal section of head of 

 Myrmica lei'inodis worker. (Janet.) cc. 

 Central body of brain ; cf>. pedunculate 

 bodies ; ol, optic lobe ; on, optic nerve ; e, 

 eye ; lo, olfactory lobe with glomeruli ; mg, 

 mandibular gland ; rs, reservoir ; cr, cri- 

 bellum : </, ducts from gland cells ; tr, 

 tracheae : mx, maxillary gland ; Ibr, labrum : 

 me, buccal cavity. 



