It is not necessary in Florida, but it could be hotter there. I have a couple boxes with dark migratory tops and they are fine. If you have a telescoping cover, you will need an inner cover so they do not glue it down. If you use a migratory there is no issue. One of my students runs insulation over the migratory with metal to protect it. In Honduras they use migratory covers with the metal and an air gap to dissipate the heat. I think Honduras might be hotter than Texas.
I'm about 100 miles south of you. I use a telescoping cover with an inner cover. I put a couple of 3/4" blocks at the front of the inner cover to allow a little more air circulation...also tilts the cover slightly back for rain run off.
I assume you are talking about using an inner cover with a telescoping cover. If you use a migratory lid, no inner cover is needed, and no, they won't get too hot. If you are worried about too much sun, shades would be the way to go.
I know one guy who uses the inner cover with the hole plugged for his summer cover. It collects a bit of water, but doesn't seem to hurt. I know others that just use a 16 x 20 piece of cheap plywood for a cover. Works, but looks like crap.
If you already have telescoping covers, and use them without inner covers they can be a real btch to get off once they are glued down. If you don't want to spend the extra money on inner covers (they are nice), here's a couple of alternatives:
Heavy plastic sheet just a little bigger than hive top (20 x 24, say). Or, -- burlap sacks make real good inner covers, and they insulate too. A piece of 3/8 plywood 16 x 20 will work and is cheap enough. No need for a hole, unless for a bucket feeder.
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