104 BULLETIN 108, UNITED STATES NATIONAL MUSEUM. 



Metamorphosis. 



The newly hatched forms of all castes of termites were formerly 

 considered to be alike, or "undifferentiated," but the work of Thomp- 

 son (1917) has disproved this. Thompson states that at the time of 

 hatching there are two kinds of nymphs^ — the "reproductive" and 

 the "worker-soldier" nymphs, which develop into the fertile or 

 reproductive castes, and the sterile castes, and which may be distin- 

 guished by internal differences in the brain, the composite eyes, and 

 the sex organs. 



The metamorphosis of termites is of the type known as incomplete 

 or ametabolic metamorphosis, and, in the case of the worker caste, 

 there is very little external change during the development, the 

 newly hatched worker-soldier njrmph being active and similar to the 

 adult worker in all but size. The development of the worker is, 

 therefore, a gradual growth, the semitransparent large-headed 

 n3^mphs imdergoing several molts which are preceded by temporary 

 periods of inactivity known as quiescent stages (Strickland, 1910; 

 and Snyder, 1913 and 1915). 



The exact number of molts of the castes of any Nearctic species of 

 termite is not kno^^^l, and further investigation of tliis subject is 

 needed. 



In the soldier and "nasutus" caste the metamorphosis is marked 

 by very considerable external and internal changes. In Reticuli- 

 termes the soldier caste is differentiated late in the development, the 

 young soldier with rounded head and but slightly elongated jaws 

 emerging after a quiescent stage of short duration from a workerlike 

 skin (Snyder, 1913). Both workers and soldiers complete their 

 development within one year. 



The development of the small-headed or reproductive nymphs 

 is also gradual, lasting about two years, and is marked by the external 

 changes caused by the growth of the wing pads and wings. 



In all stages of the development of our native termites the insects 

 are active, except for these quiescent stages of comparatively short 

 duration. Furthermore, in all these developmental stages, unlike 

 in insects with complete metamorphosis, the adult, or what may be 

 superficially termed the "antlike " form, may be distinguished. 

 Castes of Termites or the Termite Colony. 



In termite colonies or social communities, as in the colonies of ants, 

 there are several different forms or castes of adult insects besides 

 eggs and the developmental stages of the different castes in various 

 stages of growth. 



> The term "nymph" is used, in the sense of Thompson (1916), to denote any developmental stage of 

 insects with incomplete metamorphosis, instead of the two terms "larva," and "nymph," which were 

 formerly used to denote, respectively, nymphs without the beginnings of wing pads, and nymphs which 

 had developed the beginnings of wing pads. 



