Supposedly Flightless Fruitfly Madness

[chanda]

"A culture of vestigial-winged fruit flies is very handy for starting hatchling tarantulas. Unfortunately, fruit flies are deficient in amino acids so they are not suitable to feed as more than half the diet of a growing tarantula...Spiders fed too long on fruit flies alone develop molting problems and curly legs, which is too bad as fruit flies are so easy to raise...".

Not only that, but all of the spiders I've raised on flightless fruit flies have completely failed to develop wings...

 

[JanPhilip]

I get it from arachnologist Samuel Marshall, who states:
"A culture of vestigial-winged fruit flies is very handy for starting hatchling tarantulas. Unfortunately, fruit flies are deficient in amino acids so they are not suitable to feed as more than half the diet of a growing tarantula...Spiders fed too long on fruit flies alone develop molting problems and curly legs, which is too bad as fruit flies are so easy to raise..."

That is very interesting. I do not know where he gets his data from though, so without some sort of experiment I am still somewhat reluctant to believe this.
Only feeding a single type of pray might significantly decrease the lifespan of your spider, even if it is crickets only (source). It is very clear that it is important to vary the diet if you want to increase the chance of your spiders surviving to adulthood. Also, raising the prey with proper food is extremely important, especially for spiders where adding supplements externally probably wont be as helpful as for other animals. Poorly fed prey will have a large effect on the growth rate as well as the chance of your spider surviving to adulthood (source). It has also been shown that feeding dead prey wont affect the spiders negatively, and in some cases perhaps even be beneficial (source). So if you remain skeptical of fruit flies, there is nothing wrong with killing or cutting up larger prey items. I just think the decision should be based on proper information. Personally, I am especially skeptical of feeding mainly meal worms or super worms, as these are super high in fat, but poor in other nutrients (see previous post) and it was shown that a high-fat diet is very unhealthy (source).
A bit (further) off topic just because I came across it and found it interesting: Feeding more might increase the size of the mature spider, but does not really affect the time it takes to mature, all without affecting survival rates (source).

Lastly, all of these experiments were done with wolf spiders (Lycosidae), and even between closely related species different prey has different effects, depending on the life history of the spider. Therefore, this might all not translate 1:1 to tarantulas, but I still think the general message should be correct. I also think we need to be careful to make to definite statements based on own observations, as these are mostly restricted to very few specimens and with animals that produce the amount of offspring that most spiders do, there are always some that do not make it, no matter how good the husbandry might be.

Also, sorry for hijacking the thread. It is a topic which interests me and I have had a lot of discussions about with other keepers.