PROC. ENT. SOC. WASH., VOL. 22, NO. 6, JUNE, 1920 147 



may be observed with partial pigmentation to the chitinized parts, but with 

 the wings partially unfolded, or unfolded but crumpled wings, or merely the 

 long opaque wing pads of the mature nymph before the last quiescent stage 

 and molt. Other individuals that may have the mature body pigmentation, 

 but distorted or poorly developed wings, or even wing-pads, emerge with the 

 normal winged adults at the time of the swarm. 



"It was formerly explained that these abnormally developed individuals 

 were merely abnormalities due entirely to unfavorable conditions of moisture. 

 Now, however, when considered with certain 'intermediate' forms, these ab- 

 normalities may be termed fluctuating variations or mutations from the nor- 

 mal winged reproductive forms, (Thompson and Snyder, 1919). These ab- 

 normal forms, together with the 'intermediate' forms represent almost a 

 complete series beginning with normal wings and ending with the apterous 

 reproductive form, a large intergrading series. On these intermediate forms 

 the length of the wing pads ranges from the long wing pads of the nymphs 

 of the first form to vestigial buds. 



"These abnormalities and 'intermediates' have partial pigmentation to the 

 body, and the intermediates have various stages of eye development, ranging 

 from partial mature pigmentation to the eye to merely traces of the eye. 



"In the forms which develop abnormally at the time of the quiescent stage 

 and final molt of the nymph of the first form there are various forms which 

 might be compared to the 'club,' 'vestigial,' and 'stumpy' wings of the 

 mutants of Drosophila melanogaster (ampelophila). 



"The writer has, unfortunately, only preserved a small series of these ab- 

 normalities which occur 'wild,' or in nature, as well as in rearing cages or 

 artificial colonies; these are mostly females 5 females and 3 males." 



It will be noted that there is not only much variation in the 

 development of the eye of the intermediate reproductive adults 

 (near the stable second form adults), but there is also much range 

 in the intensity of body pigment. 



To summarize, from the viewpoint of the mutation theory, all 

 of these problems, involving the social system and the highly 

 specialized castes, which can not be satisfactorily explained by 

 the evolutionary theories of Lamarck and Darwin can be ex- 

 plained by DeVries' mutation theory. This is the view held by 

 many modern workers. 1 



A similar view of the origin of castes is suggested in a more 

 recent paper by Imms (1919). 



The second and third reproductive forms would be chiefly pro- 

 gressive mutations, also the workers and the two types of sol- 

 diers; there has been a loss of characters. The workers and sol- 

 diers have also gained characters which are often useful, as seen 

 in the legs, heads, mandibles and nasuti. Now a mutation is 

 not necessarily useful, but a Darwinian variation must be useful. 



1 1903. Morgan, T. H. Evolution and adaptation. New York. 



