CHROMOSOME NUMBER POLYMORPHISM IN 
THE SAWFLY JANUS INTEGER 
(HYMENOPTERA, CEPHIDAE)* 
By R. H. Crozier and E. F. Taschenberg 
Department of Zoology, University of Georgia, Athens, Georgia ; 
and Vineyard Laboratory, New York State Experiment Station, 
Fredonia, New York. 
Introduction 
The Symphytan family Cephidae has a special significance in the 
study of the evolution of the Hymenoptera, as it is belived to be 
the group closest to the stem from which the Apocrita evolved. The 
chromosomes of only one cephid, Cephus cinctus, have been de- 
scribed previously (Mackay, 1955) ; the Cephidae are therefore an 
important but cytogenetically little-known group. 
Methods 
Male pupae of Janus integer were obtained by allowing virgin 
females to oviposit on caged currant bushes from which all the pre- 
vious year’s growth had been removed. 
Chromosome preparations were made from pupal or prepupal 
testes using an air-drying technique (Crozier, 1968, 1970). Each 
prepupa or pupa was punctured using a minuten pin and placed with 
the puncture touching a drop of a 0.05% solution of colcemid in an 
insect Ringer solution and left overnight. The next day the testes 
were dissected out under a 1% w/v sodium citrate solution and left 
in the solution for 20 minutes; they were then fixed in 3:1 meth- 
anol-acetic acid fixative for at least 45 minutes. The cells were 
dissociated using a drop of 60% acetic acid on a warm slide and 
the suspension spread using further methanol-acetic fixative before 
being dried by an air-flow and stained using aceto-lactic orcein. The 
preparations were dehydrated and mounted in ‘Euparal’. 
The chromosomes of intact cells were counted using a hand 
counter. If a majority of cells had shown the same number after 
20 cells, and none had been found with a higher number, that num- 
ber was taken to be the chromosome number of that individual. 
Otherwise, further cells were counted. 
Results and Discussion 
The karyotypes of eight male Janus integer were determined. Two 
* Manuscript received by the editor March 3, 1972. 
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