Cfrgtkky

If by ‘from space’ you mean dropped from above the Karman line: then any. Humans have skydived ‘from space’.

If, however, you mean any other definition of ‘from space’ then... Erm.. None really.

The issue here is one of velocity. If by ‘from space’ you mean ‘in-orbit’ or ‘after being captured by earth’ then your bugs will be hitting the atmosphere at speeds on the order of 10km/s.

The heat on re-entry is caused by compressive heating, not friction. Essentially all the air can’t get out of the way because the object re-entering is moving too fast, so it gets squished up and (because physics) heats up too.

If they don’t cause compressive heating and (briefly) turn into glowing bug-cinders then they’re still going to squish up all that air, and also squish up all of themselves.

If they don’t get burnt to a very well-done cricket-croquette or splattered on the windshield of Mother Earth then they still have to deal with the air around them rushing past at hypersonic speeds. Legs, wings, shell casings; anything that is a tiny crevice will get them sent into a high speed tumble and also torn apart.

There is no size of bug that can survive re-entry as it’s commonly understood. The speeds involved are just a bit more than biology was designed to handle.

Almost all of them. The terminal velocity of most insects isn't fast enough to generate the friction required to burn. The only issue would be a sustained lack of Oxygen, likely for several minutes depending on the height dropped, in the upper atmosphere. but seeing as you've hand-waved that problem it looks like your bugs are going to be just fine.

Edit: Just FYI this statement only applies if the insects are dropped from a stationary position (or at least relatively slow moving position) If they are traveling at 1000s of km/s they will likely be burnt to a crisp the moment they are released from whatever drop pod they are in.

As expressed in previous answers and comments, this is primarily an issue of atmospheric entry velocity, rather than insect biology. At least some naturally-occurring insects are able to withstand hard vacuum, so it's extremely plausible that insects genetically engineered for that specific purpose would also be able to do so.

The entry velocity problem is (relatively) easily resolved by dropping the insects from a craft which is traveling at a low velocity relative to the upper atmosphere at the time of the drop. To do so, it cannot be in anything resembling a stable orbit[1], so it will need to be under active thrust to avoid crashing into the planet, unless your setting includes anti-gravitic technology.

This would be a high-fuel-expenditure operation, but that probably isn't a major issue for a civilization which conducts interplanetary operations frequently enough to have made the effort of creating genetically-engineered planetary assault insects, nor for any civilization capable of interstellar travel. It would also most likely reveal the presence of the dropping craft to observers on the surface, as they would be able to see the exhaust flare.

[1] If it were in anything resembling a stable orbit, then it would, by definition, need to be moving at orbital velocities, and the bugs would instantly burn up on contact with the atmosphere.

They Grow in Pods

Since you're doing genetic engineering anyway, have each insect grow in its own little cone-shaped pod. Even if dropping from a point that is stationary relative to the atmosphere, I think your insects will reach hypersonic velocities before aerodynamic drag is high enough to slow them down (see some math below, and the transitional drag paper below for more math and some pretty graphs). They will still experience heating, and may tumble hard without some aerodynamic help. They're also going to have to deal with subzero temps after they do slow down, which an insulating pod will help with. You could optionally make the pod vacuum-tight as well, with a little vent or trapdoor that seals from the inside with some sort of secretion. The little pod can be ablative -- it turns out that the material emitted from ablation helps slow down at these sizes (also in the paper).

Hypersonic Housefly

As I mention above, deployment speed may not matter much. The potential energy even at a "stationary" point above Earth's gravity well is impressive; all that potential energy will get converted to kinetic on the way down.

Play with calctool, referencing upper atmosphere models and various drag coefficients to get a better feel for this. For example, calctool will tell you that the terminal velocity of a 10 mg housefly at 100 km altitude is 6213.60 m/s (assuming a drag coefficient of .5 and a cross-sectional area of around 20 mm^2).

But, as @JanHudec points out below, our fly won't reach terminal velocity at 100 km (but will hit terminal at slightly lower altitudes). The speed it will reach at 100 km depends on how high it's dropped from. If we somehow arrange for a stationary release at 600km altitude, then gravity will still have the fly screaming straight down at close to 3000 m/s as it enters the upper atmosphere at around 100 km.

The NASA Glenn Mach number calculator tops out at 76 km, but it tells us that 3000 m/s at that altitude is just above Mach 11. At hypersonic speeds, the fly will experience compressive heating from its own shock wave. The GRC stagnation temperature calculator also tops out at 76 km, but should help with heating estimates.

For the several seconds it takes to slow down, this fly's temperature is going to be somewhere above the boiling point of steel. The transitional drag paper tells us that something the size of a housefly will slow down sooner if ablating though, which again puts it back into a pod.

By the time our fly is down around 80 km, after dumping all that energy into heat, it's slowed to the terminal velocity for that altitude of around 1000 m/s, or about Mach 4. It looks like the fly finally goes subsonic and starts cooling off around 50 km.

At 20 km altitude, our fly will finally be drifting down at a lazy 14.4 m/s, but now has the opposite problem, because at that altitude the ambient temperature is around -67 C. After a few seconds of blistering heat, it's now going to spend maybe half an hour drifting down at subzero temps.

LEO orbit is typically around 7000 m/s anyway, so in summary you may not be gaining as much as you'd think by dropping from an atmo-stationary point. Because insulation matters more than deployment speed, with a pod you could go back to dropping from a normal low orbit so you can get better swarm distribution, which dropping from a stationary point won't let you do.

Further Research

For more background on speeds and conditions at higher altitudes, look for papers like The Transitional Aerodynamic Drag of Meteorites -- that paper, for instance, covers micrometeorites (particle sizes of a few microns), as well as mesometeorites (particle sizes of a few millimeters). Insects are going to perform somewhere in that size range.

For lower altitudes and speeds, take a look at jumps like Felix Baumgartner's, and subspace balloon flights like those of JP Aerospace -- they've learned a lot about the environment around 100,000 feet, but you'll need to get down to that altitude first.

Ok. I’m a scientist of Psychology and curious hobbyist of others so please forgive my ignorance at this subject level. But, I’m just going to break this down in laymen terms for the general readership that may stop by and please feel free to comment for better or worse 😁 be gentle..

If a winged insect weighing of less that a 10 milligrams as does a common average housefly; Flys up to only the height of where the air is 45 degrees, they will severally slow down due to imparement and die when they fly around a temperature below 32 which is at the height of some low fog. https://www.weather.gov/jetstream/layers This site will show you the actual information and if you dig farther you can see in your area of the world, how high Flys’ Fly. So No it can’t and it could even if it could’nt even due to biological size and mass.

The moment it was released into exosphere, after about 10 seconds or so it would vaporize, human skin and the tissue underneath begins to swell as the water in your derma (skin) layers begin to vaporise due to the absence of atmospheric pressure. Thats a human with pretty tough skin. the human body is capable of slowing down radiation. Passing through its body. It does make its way through it but by then we are dead. A common fly is made up of primarily liquid so as a human, it too would vaporize, but much faster due to its 10 milligram weight.