Take a close look at photos of plants having sticky defensive glands such as Stylidium. Captured insects are stuck on the glands and not even in contact with the leaf surface.
There is a prevalent misconception about such sticky glands. The retentive glands of pseudo-carnivorous plants resemble those of Byblis and Pinguicula. Unlike in Drosera, the retentive glands of these plants only secrete glue and do not absorb. Absorption in Byblis and Pinguicula is carried out by the leaf surface through the digestive fluid secreted there.
Carnivory in Byblis linifolia is rather primitive. I have observed while growing the plant that there is no secretion of digestive fluid from the leaf surface unless the plant is in high humidity. Also note that the majority of the retentive glands are too long stalked and insects caught on them will be suspended well above the leaf surface and so unavailable for digestion. I suspect that these excessively tall retentive glands are primarily defensive. It seems to me that carnivory in this species is more of a side benefit of the plant’s defensive weaponry.
There is a prevalent misconception about such sticky glands. The retentive glands of pseudo-carnivorous plants resemble those of Byblis and Pinguicula. Unlike in Drosera, the retentive glands of these plants only secrete glue and do not absorb. Absorption in Byblis and Pinguicula is carried out by the leaf surface through the digestive fluid secreted there.
Carnivory in Byblis linifolia is rather primitive. I have observed while growing the plant that there is no secretion of digestive fluid from the leaf surface unless the plant is in high humidity. Also note that the majority of the retentive glands are too long stalked and insects caught on them will be suspended well above the leaf surface and so unavailable for digestion. I suspect that these excessively tall retentive glands are primarily defensive. It seems to me that carnivory in this species is more of a side benefit of the plant’s defensive weaponry.