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CARNEGIE INSTITUTION OF WASHINGTON. 



sis of the causes of this decline in the rate of pulsation with the decrease in 

 muscular tissue involved was made at this time. 



Breeding Experiments ivith Porto Rican Lepidoptera, by John H. Gerould. 



I studied the insect fauna of the island with a view to extending my experi- 

 mental work in breeding polymorphic species. These investigations aim to 

 throw hght on the laws of heredity and the evolution of new species. Mr. 

 Eugene G. Smyth, entomologist of the experiment station at Santa Rita, 

 near Guanica, with the cooperation of Mr. F. T. Maxwell, general manager 

 of the Guanica Central, generously offered the use of his insectary and assisted 

 me in many ways. 



Preliminary experiments were begun in mating and breeding pierid butter- 

 flies of the genera Terias and Callidryas. Two species of the former occur 

 together in nearly equal abundance at Guanica (T. euterpe and T. palmyra), 

 which afford excellent possibilities for experiments in hybridization. Their 

 pronounced and distinctive color-patterns, small size, and easily controlled 

 mating make them especially favorable for experimental breeding in large 

 numbers. 



After leaving Guanica and the south coast, I spent several days in the 

 mountainous interior, first at Ad juntas, where I met and cooperated with Dr. 

 F. E. Lutz and Mr. A. J. Mutschler, of the American Museum of Natural 

 History, who were engaged particularly in collecting Hymenoptera and Cole- 

 optera, and subsequently at Maricao. Still later I visited the experiment 

 stations at Mayaguez and at Rio Piedras, where, through the kindness of the 

 entomologists, Messrs. R. H. Van Zwalenburg of Mayaguez and G. N. Wal- 

 cott of Rio Piedras, I examined the collections of Porto Rican insects. 



An inviting object for investigation observed at Adjuntas and Maricao is 

 Leptalis spio, the pierid ''mimic" of Heliconius charitonius. The latter is 

 abundant in the shade of coffee and banana trees covering the glens and hill- 

 sides. In the same regions, less abundantly, with similar habits of flight, 

 occurs the "mimic." The specimens observed and collected were not, how- 

 ever, of the color of the hehconid "model," yellow and black, colors that are 

 possessed in other parts of the island by the "mimic," but of orange and black. 

 This orange and black variant of Leptalis spio, well known to entomologists, 

 is possibly, and indeed probably, the result of a mutation that may have some 

 time taken place in the stock of the yellow and black "mimic." If so, this 

 would be an example of a mutation tending to destroy rather than create 

 "mimicry." The genetics of the two varieties of this polymorphic so-called 

 mimic present an inviting field for investigation. The genetic relationship 

 of the two varieties to one another, their bionomic relation, if any, to Heli- 

 conius charitonius (the "model"), the life history of which should be studied 

 simultaneously with that of Leptalis spio, are matters of unusual and manifold 

 interest. 



