86 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



Professor Quaintance a vote of thanks for the efficient manner in 

 which he managed the affairs of the society and for his timely and 

 most interesting address. Carried. 



Mr. Gahan presented the following paper: 



SOME NOTES ON THE PALPI OF APHIDIIN^. 



BY A. B. GAHAN, Maryland Agricultural Experiment Station. 



In a previous communication before this Society, the writer 

 called attention to certain variations in the number of antennal 

 segments in various species of Aphidiinse. Among other species 

 studied with regard to this variation was Diaeretus rapce Curt., 

 the common parasite of Aphis brassicw. 



Recent study of the same species has brought to light another and 

 more surprising variation, this time in the number of segments in 

 the maxillary palpi. While apparently the palpi are more fre- 

 quently four- segmented than otherwise, in a series of one hundred 

 and fifty or more specimens there appear to be almost as many in 

 which they are distinctly three-segmented. Not only is this true 

 but several specimens were observed in which one palpus was 

 plainly four-segmented while the other had but three complete 

 segments. 



In cases in which the number of segments differs in the two palpi 

 of the same individual, it is apparent that the difference is due to an 

 imperfect separation of the third and fourth joints in one palpus. 

 The point at which the division should have occurred is usually 

 indicated by a more or less distinct notch on one or both sides of 

 the segment. In specimens having both palpi three-segmented, 

 usually no such notch is present but the third segment is generally, 

 though not always, somewhat more elongate than is the case in the 

 four-segmented palpi. 



That this is really a variation within the species seems certain, 

 since a small series of specimens, all the progeny of a single female, 

 shows individuals having three-jointed palpi as well as others in 

 which the palpi are four-jointed. That it is not merely an acciden- 

 tal variation is proven by the fact that in several large series of 

 specimens reared from the cabbage aphis on widely different dates 

 the same variability occurs. 



Both sexes vary alike and in about the same proportion, so that 

 -the differences are in no sense sexual. 



In view of the fact that some importance has been attached by 

 Haliday, Marshall and others to the number of palpal segments, 

 in the classification of the Aphidiinae, it is of some interest to know 

 whether the same variability occurs in other species and genera of 



