PROC. ENT. SOC. WASH., VOL. 22, NO. 6, JUNE, IQ2O 145 



whereas the second form adults needed the care and nourishment 

 usually afforded them by the workers. Possibly the jaw muscles 

 in these young second form adults had begun to degenerate, 

 through disuse in masticating wood, as happens later, (Thompson 

 and Snyder, 1920). On account of lack of specimens and oppor- 

 tunity to collect others at the proper season, no further crossing 

 was attempted. It is believed that second form males like the 

 females would have succumbed, without the workers. Never- 

 theless, further efforts at crossing the different reproductive types 

 will be made, with species of several genera. 



Summary and Conclusions. 



In the preceding pages, the three types of colonizing reproduc- 

 tive forms of termites, and the nymphs from which they develop, 

 have been described; "intermediate" forms have also been dis- 

 cussed. 



Data on the occurrence and habits of these different reproduc- 

 tive forms have been presented. 



The different methods by which these three reproductive forms 

 establish new colonies have been outlined and the progeny of these 

 forms described. 



The results of experiments in breeding and cross-breeding have 

 been used to supplement observations on these reproductive forms 

 made in the field. 



It seems to the writer not unreasonable to conclude that the sec- 

 ond and third reproductive forms, as well as the intermediates, 

 in termites are mutations! They, so far as is known, breed true 

 to type; in this case then, all the castes are mutations from the 

 parent first form, and a plausible explanation for the phenomenon 

 of polymorphism is afforded. As has been shown before, (Thomp- 

 son and Snyder, 1919 i "A gradation of characters can be traced 

 throughout the series." "These castes might be 



interpreted either as gradations in a series of continuous or fluc- 

 tuating variations, or as a series of regressive mutations, i. c., 

 mutations formed by the loss of characters, comparable to the 

 series of mutations found in Drosophila." "Should the 



former prove to be the case, then transitional or intermediate 

 forms between the existing castes should be expected, but it must 

 be remembered that mutations also may be arranged to form a 

 structural series, even though they may not have originated in this 

 order," (Thompson and Snyder, 19111). As has been shown, 

 rather few intermediate forms have as yet been found. 



The sterile worker and soldier (also nasuti) castes and colony 

 life have existed among termites since the late Tertiary period, 

 for these forms are found as fossils in gum copal, indicating an 



