Advice or help with sling escaping from this container

[Dangergirl]

OK, I have lost 2 fasciatum slings from this container ... the third is OK and has burrowed under the bark. I just cant seem to figure out how they got out ... :? Maybe someone else can see what I'm missing ?? (and each was housed in seperate containers)

Perspex box with reasonably tight fitting lid :
Measuring 10X10cm (4X4inches)

Size of spiderling

 

[KoriTamashii]

For some reason to me from the pic you posted, it looks like there's a gap between the overlapping lip part of the lid and the side of the box. :?

 

[AmbushArachnids]

Could the T have pushed the lid off? I dont see any gaps. :?

 

[Midknight xrs]

the vent hole on the top looks like there's a large enough gap to get out.

 

[christianD]

escape

the vent hole on the top looks like there's a large enough gap to get out.

agreed. otherwise if its not glued in and just sitting in there the T coulda pushed up under it. I watched my .5 in G Rosea squeeze through the top of her deli cup after I bought her. didnt look like she had any trouble.
hope you can figure it out though. If it happens again or if you want to avoid it (which you probably do) The Container Store is where I go for my enclosures for slings. they have some really good rectangular prisms and cubes. just find a dremmel and drill some holes in the top and a few in the sides, fill with suitable substrate and insert T.