The answer to the question is 9.

Solution:

Let Pugsley has 'x' spiders and Wednesday has 'y' spiders.

Let us denote Pugsley as P and Wednesday as W

After P gives W 4 spiders,

Number of spiders with each of them,

P= x-4

W= y+4

According to the question,

W=5P

So, y+4 = 5*(x-4)

5x-y=24 ---- (Equation 1)

Now, W gives 4 spiders to P,

P= x+4

W=y-4

According to the question W has still 4 more spiders than P, So we need to add 4 to P to equalize

P+4=W

(x+4) +4 = y-4

y=x+12 ---------(Equation 2)

Solving (1) and (2)

x= 9 , y=21

Verification

P= 9 ; W = 21

9-4= 5

21+4= 25 and 25 = 5*5.

Also, 9+4= 13

21-4= 17 and 17= 13+4

Thanks