The spell Stone Spiders (FRCS, p. 75) reads:
You transform 1d3 pebbles into stone constructs that resemble monstrous spiders. The constructs can be any size from Tiny to Huge as you decide, but all the constructs you create must be the same size. The constructs have the same statistics as monstrous spiders (see Appendix 2 in the Monster Manual) of the appropriate size, except as follows:
Their natural armor increases by +6.
They have damage reduction 30/+2.
Their poison has a Fortitude save DC of 17 + your Wisdom modifier. Initial and secondary damage is 1d3 points of temporary Strength damage.
This seems pretty straightforward. But the MM (p. 307) says on constructs:
Features: A construct has the following features.
- 10-sided Hit Dice
- Base attack bonus equal to 3/4 Hit Dice (as cleric).
- No good saving throws.
Traits: A construct possesses the following traits (unless otherwise noted in a creature’s entry).
- No Constitution score.
- Low-light vision.
- Darkvision out to 60 feet.
- Immunity to all mind-affecting effects (charms, compulsions, phantasms, patterns, and morale effects).
- Immunity to poison, sleep effects, paralysis, stunning, disease, death effects, and necromancy effects.
- Not subject to critical hits, nonlethal damage, ability damage, ability drain, fatigue, exhaustion, or energy drain.
- Immunity to any effect that requires a Fortitude save (unless the effect also works on objects, or is harmless).
- Not at risk of death from massive damage [...]. Immediately destroyed when reduced to 0 hit points or less. [...]
The MM also attributes bonus HP to constructs based on Size.
If you apply all these traits and features to the Monstrous Spider, you get a creature that in almost no way has "the same statistics" of the Monstrous Spider.
A Huge "Stone Spider" would look like this:
Init +3 (+3 dex)
AC 22 FF 19 Touch 11 (-2 size, +3 Dex , +11 natural)
HP: 84 (8d10+40)
Fort +2 (immunity to all effects unless effecting objects) Ref +5 Will +2 (immunity to all mind-effecting effects)
Speed 30 ft. (6 squares), climb 20 ft.
Base Atk +6 Grp +18
Attack: Bite +8 2d6+6 plus poison DC 23 (1d3 Str/1d3Str)
Full Attack: Bite +8 2d6+6
Space 15 ft. (3 squares) Reach 10 ft. (2 squares)
Abilities Str 19(+4) Dex 17(+3) Con -- (+0) Int -- Wis 10(+0) Cha 2(-4)
Darkvision(Ex): 60 ft.
tremorsense(Ex): 60 ft.
Low light vision
Immunity to all mind-effecting effects, poison, sleep, paralysis, death, stunning, disease, necromancy, critical hits, non-lethal damage, ability damage, ability drain, fatigue, exhaustion, energy drain all effects that require a Fort save (unless affecting objects).
On the other hand: If you took the spell literally, you would get a construct with a Constitution score, something very strange indeed.
Do you really go with the Monstrous Spider stats? Or do you apply construct traits to the Monstrous Spider (apart from the DR which is explicitly set in the spell)?