Certainly if you are planning to go on the offensive with your Scarab swarms you want that Spyder farm- two or three dedicated Spyders per swarm, pumping out 2-3 bases per turn as fast as you can roll those dice. Hopefully you have taken that into consideration and adjusted your list for the use of the heavy support slots taken up by your Spyders.
The internet seems to be in love with this right now, but what about a scaled back defensive use for them?
If you are using your Scarabs in a more passive manner – to block off sections of table – threat bubbles to direct the movement of your opponent to allow the rest of your army to accomplish the mission goals then do you really need all those Spyders?
In cover and with less direct losses one Spyder might be all you need and could present an interesting choice – on par with results if you had the farm of 6-9 of them.
I promise this isn’t turning into a Scarab article, but the two are linked!