A MUTATION IX THE MOTH-LIKE FLY (PSYCHODA 



ALTERNATA) AND THE METHOD OF 



ITS TRANSMISSION. 



C. L. TURNER, 

 ZOOLOGICAL LABORATORY, BELOIT COLLEGE. 



I. LIFE HISTORY AND GENERAL FEATURES OF THE NORMAL FLY. 



The Moth-like Flies are inconspicuous insects about 2 mm. in 

 length which breed in water, decaying vegetation and in manures. 

 They have been little studied and consequently the life histories 

 of only a few are completely known. In one or two instances 

 they have been observed under laboratory conditions for two or 

 three generations with the end in view of determining the lengths 

 of the various stages of the life histories. There is no record, 

 however, of their being carried under such conditions for more 

 than a few generations. 



During the past year the writer has reared successfully two 

 species (Psychoda alternata and Psychoda minuta] and one of the 

 two has proved itself to be an excellent subject for studies in hered- 

 ity. A mutation has arisen in Psychoda alternata and the method 

 of its transmission determined. A full account ! of the life histor- 

 ies and of the general features of the two species mentioned has 

 been offered in a previous paper so that no extended account will 

 be necessary here. It seems necessary, however, to repeat the 

 account in so far as it has to do with the mutation. 



Eggs are laid upon moist manure by the females and within a 

 few days they hatch producing active, feeding larvae resembling 

 those of midges. The larva' possrss pigment in two forms. 

 Chitinous plates are present on the dorsal side of the last two or 

 three segments (Fig. I, C.P.} and a heavy chitinous sheath covers 

 the head and the last segment (Figs, i and 2). These plates are 

 light brown in the young larvae but they grow darker with age. 

 The other pigment is reddish brown in color and is found in the 

 ocelli (Fig. 2, Oc.) and the Malpighian tubules of the larvae 

 (Fig. i., M.P.T.). 



1 The Psychodidae as Subjects for Studies in Breeding and Genetics, Amer. Nat., 



Vol. LVII. pp. 545-558. 



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