Chorthippus parallelus (Zetterstedt) is a very common meadow grasshopper distributed through Europe, comprising, at least, two subspecies Chorthippus parallelus widespread through Western Europe.
Fabre distinguishes between both subspecies based on some morphological differences as the number of pegs and as the colour of the hind tibiae, which is red in Chorthippus parallelus erythropus. Additional information made by Butlin and Hewitt from a hybrid zone in the Pyrenees showed that both subspecies differ in other important morphological characters such as in certain enzyme loci, as well as in certain ethology characters, such as the courtship song. In the last few years molecular markers were used in order to differencied both subspecies, but these are small  or there are not differences . The main differences, found between both subspecies, are restricted to the Sex-chromosome in the heterochromatin localisation and the presence or absence of a nucleolus organiser region (NOR) .
During the ice age these subspecies were separated and diverged in allopatry in zones more temperate in the South of Europe and North of Africa. In the post glacial age both subspecies expanded into Europe. Chorthippus parallelus parallelus expanded through all Europe as far as the Pyrenees including the main island of the Great Britain but not Ireland island and its distribution is continuous, instead Chorthippus parallelus erythropus is restricted to the meadow mountain in the Iberian Peninsula and there is not contact between the different populations . Both subspecies contacted along the Pyrenees where they formed a hybrid zone .Some chromosomal information exists on Chorthippus parallelus parallelus populations , on Chorthippus parallelus erythropus Pyrenees populations , on the hybrid zone between both subspecies in Pyrenees and in laboratory hybrids  but nothing has been reported on the chromosomes of Chorthippus parallelus erythropus in isolated populations, except for the amount of heterocromatin . Although comparison of french populations with museum specimens from Central Spain does not show differences in respect to morphological characters , it could be interesting to study the possible variation on cytogenetical characters as in molecular markers . The Chorthippus parallelus erythropus populations, at the moment the ice were restricted to the high mountains, leave the low land and move up the mountains, losing the contact and the possible gene flow between the different populations, localised on the Sistema Central (central Spain), the Sistema Cantabrico (North-West of Spain), the Sierra Nevada (South Spain) and the Pyrenees (Noth-East), and star to diverge between them, at the same time that the Pyrenees populations meet with the populations of Chorthippus parallelus parallelus and make a hybrid zone.Two hundreds adult males of Chorthippus parallelus erythropus were collected from natural populations in the Sistema Central in Spain. Testes were removed and fixed in 3:1 ethanol-acetic acid. Air dried chromosome preparations were made by squashing tissues in 45% acetic acid, freezing them in liquid nitrogen and removing the coverslip with a razor blade. The Giemsa C-banding method was carried out according to Rubio and Ferris  and the silver staining method was performed according to the method described by Rufas and Gos¨˘lvez adding, in some cases, a pre-treatment with double standard saline citrate solution to obtain a better resolution in the position of the active NORs . Fluorochrome banding with chromomycin A3 (CMA3) was obtained according to Schweizer  and Bella et al.The male chromosome complement of Chorthippus parallelus comprises 16 autosomes of different size plus one X chromosome. The three long pairs are submetacentric, while the reminder, including the X, display terminal centromeres . 
