Joined: Fri May 29, 2009 8:41 pm
It's known that flytraps evolved from carnivorous sundews; sundews (and I think this part is still theory) may have evolved from non-carnivorous sundew-like plants prior to the depletion of nitrogen in their environment's soil. The Venus Flytrap's evolution was the product of a "Hobson's choice" in which plants that did not evolve nutrient-capturing abilities in nitrogen and phosphorus-poor environments would not have survived. (citation).
I. Flytrap size and Nitrogen-feeding
In their native habitat, the flytrap diet is 33% ants, 30% spiders, 10% beetles, and 10% grasshoppers, with fewer than 5% flying insects (citation). All of these insects contain various amounts of nitrogen in their bodies, which the flytrap consumes in order to generate amino acids, proteins, and DNA (all of which affect plant mass). According to this paper, feeding on insects' nitrogen content does result in larger traps, as would be expected; 20% to 54% of a flytrap's total internal nitrogen levels come from insects. Therefore, a group of flytraps that never feed on insects will be smaller than a group of flytraps that feed on insects.
II. Insects and Nitrogen
Insects with higher nitrogen content are theoretically the "best" to manually feed an indoor flytrap. According to this paper, predaceous (predatory/carnivorous) insects have an average of 15% more nitrogen content than herbivorous insects. Spiders, predatory beetles (e.g. ladybugs), wasps, and other carnivorous flying insects have the highest nitrogen values of all insects, while insects like moths and butterflies have the lowest nitrogen value. The paper also suggested that although no data exists, there is reason to believe that collembola (springtails) may also have high nitrogen content. Since they are readily available in pet stores, I'll also note that insects such as crickets have a moderate nitrogen content as well. While not among the highest in nitrogen content, they fall well above that of moths and butterflies.
III. Adverse affect of flowering
You may have heard us mention on the forum that flytraps are "set back" from flowering because it takes a lot of energy to do so. If you've ever seen a flytrap flower stalk in comparison with the size of the plant, you can plainly see why it costs them so much energy; the thing is often as massive as the rest of the plant! In a reference to the Roberts and Oosting 1958 flytrap study, the Duke article above mentioned that the reason this setback occurs is because when producing a flower stalk, most of the nitrogen found in the plant's leaves (obtained partially from insect consumption) is removed to support the flower, which adversely affects the overall health of the plant's leaves. This is why traps often look poor during/after flowering, and why flowering often results in a higher level of dying traps. The flytrap is shedding them intentionally; they were "sacrificed" so the plant could pool together the energy required to make the healthiest flower stalk possible.
It follows that the more nitrogen (and other nutrients, including quantity/quality of light it receives daily - it's not all about the nitrogen here) a flytrap has at its disposal, the less of a setback it will suffer when flowering, and the more seed it will be able to produce.
Flowering late in the season or during dormancy can also pose a higher risk - if it's cold enough, the flytrap's flower will all but stop growing, but the process was interrupted and may not complete properly, wasting a lot of energy in the process. Flytraps evolved to flower in Spring because that's when the sun is strong enough and temps are warm enough to support it properly, and because the earlier it sets seed, the better chance the seedlings have of developing enough to survive their first winter.
An unhealthy flytrap (not enough light, or other inadequate conditions) will not only sacrifice its leaves to transfer nitrogen to produce a flower stalk, but it may do so to the point of being unable to recover from the flowering, and could die after setting seed. At the very least, it will not grow as well afterward, usually very noticeably so, for months or an entire season.
This is why there are so many flytrap care sheets out there that instruct novice growers to cut off the flower stalks - it decreases the likelihood of death resulting from flowering because 1) novices often grow flytraps in far-less-than-ideal conditions, and 2) flytraps in cultivation often have internal clocks that are "off" due to shipping/sitting on shelves that they flower at inopportune times, like during the end of the season (e.g. late October/early November) or during dormancy.
IV. Best insects to feed your flytrap due to their higher nitrogen content:
per scientific studies conducted primarily at Arizona State University
Wasps (have been known to occasionally damage traps)
Any other predaceous insect (insects that eat other insects)
V. Insects to not feed your flytrap
Known to blacken or kill individual traps:
Hard-shelled super-chitinous beetles (e.g. pill bugs, stink bugs; and snapper bugs, which are the black beetles that "snap/click" their neck to flip over if stuck upside down) *
* Ants and other chitinous bugs may only be intermittently problematic, or are only problematic for some flytraps and not others. Chitinous insects should not automatically be discounted as good food source, as chitin contains nitrogen (mealworms are a good example of this; they are chitinous but make a good food source). Your mileage may vary.
Can, and often do, chew their way out of a trap:
Wasps (in my experience wasps usually don't escape)
"Worst" insects to feed due to low nitrogen content - doesn't give the plants much in the way of nutrients compared to other bugs, but still provide the plant with some nitrogen; also, the ones listed below often kill traps due to allowing bacteria to enter the trap because the large wings generally protrude from the trap, preventing the trap from sealing properly: