Section 8 — Cytatoxonomy and Experimental Taxonomy 



Cidaria, the chromosome number of 40 Finnish 

 species has been determined, i.e. of about half 

 the number of species found in Finland. The 

 chromosome number has been determined from 

 oogenesis, but in some species spermatogenesis 

 has also been studied. The commonest (haploid) 

 number among the Cidaria species so far investi- 

 gated is 31, which is likewise the next commonest 

 number among the Lepidoptera as a whole. 

 Thirteen species had this number. Most (32, or 

 80 per cent) of the species had a chromosome 

 number between 28 and 32, like most of the 

 other groups of Lepidoptera. No species had 

 more than 32 chromosomes, whereas eight had 

 less than 28. The smallest chromosome numbers 

 found were 25 (two species), 19, 17 and 13 

 (three species and probably also a fourth one). 

 The great differences in chromosome number 

 between closely related species is of interest. 

 Such discrepancies are shown by the subgenera 

 Thera (variata and obeliscata 13, firmata 19, 

 and juniperata 30), Lampropteryx (minna 1 7 and 

 suffumata 32), and Hydrelia (testaceata 13 and 

 flammeolaria 30). The chromosomes are clearly 

 bigger in the species with a low chromosome 

 number than in those with a high one. Photo- 

 metric measurements revealed that the DNA- 

 content of closely related species is almost the 

 same, in spite of great differences in chromosome 

 number. This indicates that one chromosome of 

 a species with a low number corresponds to two 

 or more chromosomes of another one with a 

 high number. Consequently, we are not con- 

 cerned with polyploidy, although the higher 

 number is close to a multiple of the lower one. 

 It is probable that this kind of chromosomal 

 evolution — found among the Lepidoptera — is 

 rendered possible by the fact that they obviously 

 have a diffuse kinetochore. Contrary to earlier 

 assumptions, chiasmata are not formed in the 

 bivalents during oogenesis in the Lepidoptera. 

 This is especially evident in preparations stained 

 with Feulgen, when the elimination chromatin 

 contained by the bivalents in the female remains 

 unstained. 



8.22. Cytotaxonomy of Syrphid Flies. Janny M. van 

 Brink and J. W. Boyes (Utrecht, The Nether- 

 lands). 



A Xanthogramma species has five pairs of 

 chromosomes; six species of Syrphus have four 

 pairs and three others have five pairs, but in 

 one species counts of four pairs and five pairs 

 were obtained. Two Chrysotoxum species in the 

 subfamily Chrysotoxinae had five pairs. In the 

 subfamily Cheilosiinae, species in the genera 

 Neoascia, Pipizella and Cnemodon have four 

 pairs; in Rhingia, Myolepta and Cheilosia five 

 pairs; and in Chrysogaster and Liogaster six 

 pairs. One Vohtcella species of the subfamily 

 Volucellinae has six pairs but another has five 

 pairs plus a few microchromosomes. In the 

 subfamily Eristalinae, seven species of Eristalis 

 have karyotypes consisting of five metacentric- 

 subtelocentric pairs, apparently autosomal, plus 

 one or two additional pairs, or plus a peculiar 

 complex of small elements which will require 

 detailed analysis for accurate interpretation. 

 Six pairs were found regularly in species of 

 Eristalinus, Merodon, Eurinomyia, Helophilus and 

 Parhelophilus but only five pairs in Myiatropa 

 ftorea. In the Xylotinae single representative 

 species of Tropidia, Syritta, and Zelima have 

 five pairs. Many variations in chromosome 

 morphology were also found and will be men- 

 tioned briefly. This is a preliminary report on an 

 extensive analysis of karyotypic variation in 

 this family. 



8.23. The Anal Plates of Drosophila Larvae in Differ- 

 ent Species. Suavi Yalvac (Erzurum, Turkey). 



Exposing 3rd instar larvae of Drosophila to 

 70 per cent alcohol causes a pigmentation which 

 begins on the posterior end of the larval body 

 and spreads forward. This occurrence helps to 

 make two symmetrical plates appear around the 

 anus of the larva. Otherwise it is too difficult to 

 notice these plates because of their transparency. 



After comparing about 30 species of Droso- 

 philidae it has been established that different 

 types of anal plates exist in the larvae of these 

 flies. Some of them, like D. victoria, D. buskii, 

 D. mulleri, Chymomyza procnemius and others, 

 have anal plates so typical for their own species 

 that one can easily identify their larvae by 

 means of these plates. 



It seems that anal plates of Drosophila larvae 

 might be considered as a taxonomic factor. 



The chromosomes of 56 species of Syrphidae 

 from the Netherlands have been examined. 

 Species of most genera in the subfamily Syr- 

 phinae have four pairs of chromosomes, includ- 

 ing a small heteromorphic pair and three larger 

 metacentric to subtelocentric pairs (Platychirus, 

 Melanostoma, Sphaerophoria, Doros and Scaeva). 



8.24. Levels of Speciation and Reproductive 

 Affinities in the Willistoni Cryptic Group of 

 Drosophila. Helga Winge (Porto Alegre, 

 Brazil). 



The intercrossing of strains from different 



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