ISOPTERA 275 



The homologies of the wing-veins are discussed by the writer in his 

 "The Wings of Insects," Chapter VIII. 



The abdomen consists of ten visible segments and bears a pair of 

 two- to six-jointed cerci. The genitalia are vestigial and are 

 concealed by a backward prolongation of the sternum of the seventh 

 abdominal segment. 



If a colony of termites be examined, many kinds of individuals will 

 be found. This multiplicity of forms is due partly to the fact that 

 these insects undergo a gradual metamorphosis, and nymphs of various 

 sizes and degrees of development will be foimd running about among 

 the mature individuals. But even if only adults be considered, it 

 will be foimd that each species consists of several distinct castes. 



With the termites the nuniber of castes is greater than with the 

 social bees, social wasps, and ants; and each caste includes both male 

 and female individuals. The termites differ also from other social 

 insects in that there are at least two and sometimes three castes 

 whose function is reproduction. The following castes have been 

 foimd among these insects. 



The first reproductive caste.— At a certain season of the year, late 

 spring or early summer for omt most common species in the eastern 

 United States, there can be foimd in the nests individuals with fully 

 developed wings. These are sexually perfect males and females and 

 constitute what is known as the first reproductive caste. In these the 

 cuticula is black or dark chestnut in color, the eyes are fimctional, 

 and the wings project more than half their length beyond the end 

 of the body. A little later, these winged individuals leave the nest 

 in a body ; sometimes clouds of them appear. After flying a greater 

 or less distance they alight on the ground, and then shed their wings. 



At this time the males seek the females and they become associated 

 in pairs ; but the fertilization of the females does not take place till 

 later. It seems probable that in some cases swarms issue from 

 different nests at the same time, as we know to be the case with the 

 true ants, and that in this way males and females from different nests 

 may pair, and thus the danger of inbreeding be lessened; but 

 Holmgren and others doubt that this occurs. The greater number 

 of individuals comprising one of these swarms soon perish ; they fall 

 victims to birds and other insectivorous animals. 



Each of the more fortunate couples that have escaped their 

 enemies, find a suitable place for the beginning of a nest and become 

 the foimders of a new colony. Such a pair are commonly known as 

 the king and the queen of the colony; they are also known as the 

 primary royal pair to distinguish them from the second reproductive 

 caste. The primary royal pair can be recognized by the presence on 

 the thorax of the stimips of the wings that they have shed. 



After the nest has been begun, the abdomen of the female becomes 

 greatly enlarged, as a result of the growth of the reproductive 

 organs and their products; this is greater in certain exotic species 

 than it is in those foimd in this country. Figure 311 represents 



