The Mishna says that one is chayev for capturing the 8 sheratzim on shabbos, but for others, it depends on whether it is being captured לצורך or שלא לצורך. Rashi understands that the distinction between לצורך ושלא לצורך, when it is needed or not, is exactly the distinction made by the braisa 106b between מינו ניצוד and אין במינו ניצוד. Rashi understands that לצורך means that it is מינו ניצוד and therefore a מלאכה הצריכה לגופה for which one is chayev, but if it is שלא לצורך then it is אין במינו ניצוד and therefore a מלאכה שא"צ לגופה and therefore patur. Tosafos asks that this approach is very difficult because the opinion who exempts when it is אין במינו ניצוד is seemingly speaking even when one is capturing in order to use it and it is a מלאכה הצריכה לגופה. In other words, the concept of מלאכה שצריכה לגופה should be completely subjective and not dependent on the species that is being captured. So long as the person needs this species, even if no one else captures it, it should qualify as a מלאכה הצריכה לגופה.
Tosafos explains that there are to separate halachos. The first is that one is never chayev on אין במינו ניצוד. This has nothing at all to do with מלאכה שא"צ לגופה, rather, as the Ran explains that even R. Yehuda who is mechayev for a מלאכה שא"צ לגופה would exempt when it is אין במינו ניצוד. But when it is מינו ניצוד, the type of species that is generally captured, then according to our mishna that follow R. Shimon, we would require a מלאכה הצריכה לגופה, which is what the mishna means הצדן לצורך חייב, שלא לצורך פטור. The difference between the 8 sheratzim and all others is as Tosafos explains, the 8 sheratzim are always assumed to be צורך and a מלאכה הצריכה לגופה because they have skins that are usable, but other sheratzim are assumed to be אינה צריכה לגופה unless the person has specific intent to use it for something.
According to Tosafos it isn't clear what exactly the nature of the distinction between מינו ניצוד and אין במינו ניצוד is. It seems that it is not a general distinction that permeates all 39 melachos of shabbos (such as מלאכה שא"צ לגופה or מקלקל), rather it is a very localized distinction made within the melacha of צידה. The distinction would therefore be that the melacha of tzeida is defined by trapping species that are generally captured, but capturing species that are not generally captured is beyond the parameters of this melacha.
Based on this approach, it would have been possible that אין במינו ניצוד which is completely beyond the parameters of tzeida, is not even going to be assur m'drabonon, unlike a מלאכה שא"צ לגופה which we know is still assur m'drabonon (and only permitted in a case of tza'ar or nezek). However, Tosafos 107b deduces from the language of R. Yehoshua that even on a פרעוש which the gemara identifies a אין במינו ניצוד, there would be an issur d'rabonon to trap it - פטור אבל אסור. Although Tosafos holds that the nature of the heter for אין במינו ניצוד is not מלאכה שא"צ לגופה, rather that it is simply not included in the melacha of tzeida, it still follows the same principles that it is assur m'drabonon.
Tosafos writes that if the פרעוש is biting then one would have a right to grab it and remove it because just as we are matir מלאכה שא"צ לגופה in a situation of tza'ar, as we find on 107a by מפיס מורסא, we are also matir אין במינו ניצוד in a case of tza'ar. The Ran and Rosh justify the right to grab it and remove it differently. They say that the heter is based on the concept of מתעסק. Since the person is just trying to remove the פרעוש, not trap it, he is allowed to remove it by grabbing it since the tzeida will only be a מתעסק. Based on this heter, it should be permitted to remove even if it is not biting.