How Do Sundews Trap Insects With Sticky Glands?

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How do sundews trap insects with sticky glands? Sundews belong to the genus Drosera, and their leaves are covered with tentacles that carry glue. An insect that lands on the leaf meets that glue, and the tentacles bend slowly around it. Digestion comes after capture, and the plant absorbs the nutrients that result. The sections below explain how the glands are built, what triggers the movement, how one species adds a catapult, and where the research stops.

Quick answer

• The tentacles secrete “adhesive glue drops for attracting and capturing prey”, so an insect sticks where it lands.
• Stimulation makes the tentacles bend, and they can reach prey “from any direction”.
• Digestion follows capture, with enzymes produced by “the glue-tentacles” and nutrients absorbed afterwards.
• Drosera glanduligera adds glue-free snap-tentacles that catapult prey onto the sticky surface.

What the glands look like

The first source describes the sundew leaf as carrying “a multitude of radially symmetric, glandular emergences (glue-tentacles)”. Each tentacle is built from two parts. The source says these emergences “consist of a stalk and a terminal head”, and the head carries “the mucus-producing gland”. The sticky material therefore comes from the tip of each tentacle.

The same source notes that the sundews are “generally known for possessing active flypaper traps”. The glue-tentacles are spread across the leaf in large numbers, so the sticky surface is not limited to one spot.

How the glue captures prey

The glue is described in the second source as “adhesive glue drops for attracting and capturing prey”. Those drops are the first part of the capture. The first source says the leaves are “covered with glue-tentacles that both can bend toward and around stuck prey”. The tentacles therefore do more than hold an insect in place. They move it.

The movement is the second part of the capture. The first source says these glue-tentacles “reversibly bend toward stuck prey from any direction”. The word “reversibly” is in the source, and it describes a bending that can be undone. Because the bending is described as coming from any direction, the approach is not limited to one side of the tentacle.

What triggers the tentacles

Bending depends on a stimulus. According to the first source, the tentacles respond to “direct mechanical irritation” and to “touching of neighboring tentacles or chemical stimulation”. Touching of neighbouring tentacles is one of the named triggers.

The second source adds that “Both tentacle types are touch-sensitive”. In the species it studied, both the glue tentacles and the snap tentacles respond to touch. The sources describe the trigger in terms of touch and chemical stimulation.

The catapult case in one species

The second source studies “a sundew from southern Australia”, Drosera glanduligera. Its trap is more elaborate than a simple sticky surface. The source explains that “Prey animals walking near the edge of the sundew trigger a touch-sensitive snap-tentacle”. Those snap-tentacles are described as “glue-free (non-sticky) snap-tentacles”, so they throw prey rather than hold it.

The timing is fast. The source says the snap-tentacles “can bend within a fraction of a second”, and that an animal touching one causes a “fast catapult-action”. The prey is thrown onto the sticky part of the leaf, and then “the insects are then slowly drawn within the concave trap leaf by sticky tentacles”. The source concludes that the catapult “effectively brings prey into a more favorable position for retention”.

The first source offers the wider view of the family. It says the Droseraceae are “generally known to attract, capture, retain and digest prey animals”. The catapult of Drosera glanduligera is one variation on that general pattern. The second source contrasts it with other Drosera species that rely “solely on stickiness to catch prey”.

Digestion after capture

Capture is followed by digestion. The second source notes the first step: “Once an animal is caught and suffocated”. After that, “digestive enzymes are produced by sessile glands and by the glue-tentacles”. The source says that “the nutrients resulting from digestion become absorbed”, so the plant takes up what the enzymes release.

The first source describes the family as a group that catches, retains and digests prey. For a comparison with another group of plant responses to insects, read how plants defend against insect herbivores. For a different kind of plant movement that responds to touch, see how climbing plants sense a support with tendrils.

How long the movement takes

The movement is slow. The second source says the “whole leaf blade can undergo slow bending movements” in many species, and that the leaves “can undergo slow bending movements to enfold and retain stuck prey”. The time involved is “which can take from several minutes up to several hours”.

The first source gives a point of comparison. It says “Snap-traps can close within 100 ms at fastest”, which describes the speed of a different trap type found in other genera. The sticky sundew trap in these sources is described in minutes and hours, not milliseconds.

How we chose the sources

Both sources were fetched directly from PubMed Central, and both returned full article text. The first is a review of “trapping mechanisms in the carnivorous flowering plant family Droseraceae”, published in Plant Signaling and Behavior. The second is a research article on Drosera glanduligera, published in PLoS ONE. The first gives the family-level picture, and the second gives a close look at one species.

What we could not verify

The sources cover the mechanism well, but they leave some questions open. The limits below are stated so readers can see where the article stops.

What the sources do not say

The passages used here do not name the chemical compounds in the glue. They describe the glue as adhesive and the secretion as glistening, but they do not give its composition. The second source describes the catapult in one species and does not show that every sundew uses it. It states that other Drosera species rely “solely on stickiness to catch prey”, which marks the catapult as a special case rather than a general rule.

The sources also do not give a complete count of sundew species. The first source says that in this genus there is “a higher diversity of different tentacle types and trap configurations than previously known”, but it does not list them. Readers who need species-by-species detail should consult a current botanical reference.

Frequently asked questions

Do all sundews catch insects the same way?

No single method covers every species. The second source says other Drosera species rely “solely on stickiness to catch prey”, while Drosera glanduligera “additionally features glue-free (non-sticky) snap-tentacles”. The first source describes the sundews as “generally known for possessing active flypaper traps”, which is the general pattern.

Do the sticky glands digest insects?

According to the sources, yes. The second source says that “digestive enzymes are produced by sessile glands and by the glue-tentacles”, and that “the nutrients resulting from digestion become absorbed”. The first source uses the words “attract, capture, retain and digest prey animals” for the family.

How long does a sundew hold an insect?

The sources give a range rather than a fixed time. According to the second source, the process “can take from several minutes up to several hours”. The timing depends on the species and the prey, and the sources do not give one number for all sundews.

What triggers the glue tentacles to bend?

Touch and chemical signals trigger the movement. The first source names “direct mechanical irritation” and “touching of neighboring tentacles or chemical stimulation”.

Why does a catapult help capture?

The second source explains that the catapult moves prey into a stronger position. The source says the catapult “effectively brings prey into a more favorable position for retention”. The snap-tentacles act when an animal touches them, so the prey is thrown onto the sticky leaf before the glue tentacles draw it in.

Sources

• Trap diversity and evolution in the family Droseraceae. Plant Signaling and Behavior, 2013. https://pmc.ncbi.nlm.nih.gov/articles/PMC3907454/ (HTTP 200, opened 2026-10-28)
• Catapulting Tentacles in a Sticky Carnivorous Plant. PLoS ONE, 2012. https://pmc.ncbi.nlm.nih.gov/articles/PMC3458893/ (HTTP 200, opened 2026-10-28)