REVERSAL OF FUNCTION IN A SPECIES 

 OF OLIGARCES. 



REGINALD G. HARRIS. 

 BROWN UNIVERSITY. 



From the Biological Laboratory at Cold Spring Harbor, Long Island, X. Y. 



There occur in Oligarces sp. two methods of reproduction: 

 p.MlM-rnr-i- ami adult sexual reproduction. These two methods 

 are accompanied by a corresponding dimorphism among the 

 larva- (> t tin- species. Thus there are (l) paedogenetic l.trv.r and 

 (2) pupa-larva?. These two forms are functionally and morpho- 

 logically different. The former larvae, as the name implies, 

 rrpnxhx < I >v paedogenesis, while the latter metamorphose into 

 pup.i-. \\hich in turn become adults. Among the morphological 

 ilium MI. t-s existing between these two larval forms, three are of 

 great value in distinguishing pupa-larva.' from pa'dogenetic 

 larva-, and vice-versa, both in the laboratory un<l in nature. 

 Tht-M- are (Harris '23): 



"i. In newly born living pupa-larva? the ima.uinal discs are 

 \i-iMr. These occur laterally in the third, fourth and fifth 

 iin-nt>. They are not present in pa?dogenetic forms. 



"2, The spathula sternalis, a structure typical of Cecidoim id 

 larva', < " mis ventrally in the third segment of tin- pupa-larva- of 

 Miastor. It is not visible in newly born living pupa-larva-, but 

 after four or li\c days becomes clearly visible, due to a yellowish 

 coloration which later changes to orange and dark brown. The 

 >ha[>r of this structure differs with various species. Its function 

 is not understood. 



"3. The eyes of pupa-larvae do not touch as in pcedogenetic 

 forms but are usually clearly separated." 



These morphological differences correspond to those which 

 Springer ('17) noted in Miastor metraloas. They have been 

 confirmed in that species by the writer, and obtain in all species 

 of Oligarces and Miastor which I have observed. Though many 

 hundreds of pupa-larva?, and thousands of paedogenetic larva- 



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