It is noteworthy that both Ulysses and gypsyDv are often found in nearcentromeric sites while Penelope with one exception are not found in these presumably heterochromatic regions. Since we detected different transposition behavior of Penelope and Ulysses depending upon the strain, it was of significant interest to monitor the transcription of various TEs, including these retroelements, in the strains compared. In our experiments, we showed that Penelope and Ulysses are able to asymmetrically transpose in D. virilis parental strains even without performing dysgenic crosses that drastically increase the frequency of unrelated TE transpositions in this species. It is necessary to mention that transpositions of various TEs were detected in laboratory strains of D. melanogaster and sometimes the intrastrain mobility of certain TEs CHIR-99021 correlates with their expression level. In our study, we observed similar levels of Ulysses transcription in both D. virilis strains while this TE is transpositionally active only in strain 9. Furthermore, although gypsyDv full-size transcripts are present in both strains, this element is amazingly stable in terms of transposition. Whole-mount in situ hybridization experiments demonstrated different subcellular localization of TEs transcripts, which in general correlates with their transposition behavior in the strains studied. Contrary to D. melanogaster permissive strains, gypsyDv is weakly expressed only in the nurse cell cytoplasm and specific groups of follicular cells in both strains what correlates with its stability in the genome of D. virilis. Abundant Penelope transcripts were observed in the cytoplasm of nurse cells of strain 160, where this TE is probably transpositionally active. Furthermore, while Ulysses expression in the form of strong nascent transcripts has been detected in the nurse cells of both strains, only in strain 160 well developed foci were seen correlating with high stability of Ulysses localization in this strain. The transposition behavior of the three studied TEs apparently depends upon many factors, and is controlled at the posttransciptional level. The retrotransposon gypsyDv does not transpose, apparently due to accumulation of mutations disturbing env or other domains of this TE. However, other authors exploring the PCR technique and PTT analysis concluded that the genome of D. virilis may contain at least one copy of gypsyDv putatively encoding a complete envelope protein and, hence, we can not exclude that gypsyDv may be active in some strains of D. virilis. On the other hand, Ulysses is transpositionally active in strain 9, probably because in this strain only sense Ulysses-piRNAs are present, and the ping-pong cycle is blocked.