What are those cocoon-like bags hanging from my house?

Small grey cases stuck to the outside of your house. Roughly the size of a grain of rice, tapered at both ends, sometimes a handful and sometimes dozens across a single wall.

Customers point these out to our technicians constantly, and almost nobody knows what they are looking at.

They are plaster bagworms. They will not bite you, will not damage your structure, and are not eating your house. What makes them worth an article is that they are genuinely difficult to remove, and the reason is more interesting than you would expect.

What you are actually looking at

The case is a shelter the larva builds and carries with it. Flat, grey or brownish, a quarter to a half inch long, wider in the middle and tapered at both ends. The larva lives inside and extends partway out to move, which is why a case sometimes turns up a few inches from where you last noticed it.

Then it stops moving. When the larva is ready to pupate, it anchors the case to whatever surface it is on and stays there. That is the stage most homeowners notice, because a stationary case on a wall is more visible than one slowly relocating.

The adult is a small moth. Females are largely sedentary, and males fly, which is part of why bright exterior lighting near entries tends to concentrate them around a house.

Why they are so hard to get off

This is the part worth understanding, because it explains why the obvious approach fails.

The larva does not simply rest against the wall. It excretes a glue-like substance that bonds the case into the surface, and on stucco or textured paint that bond goes into the texture rather than sitting on top of it.

Brushing accomplishes very little. Our technicians brush at them during service and a meaningful share simply do not release. Scraping harder works, and on painted surfaces it frequently takes some of the finish with it, which trades one cosmetic problem for another.

No pest control product dissolves that attachment. Treatment addresses the insects and the conditions supporting them. It does not detach what is already glued down.

What our technicians will and will not do

Worth stating plainly rather than leaving it to be discovered.

Most pest control companies, including ours, do not guarantee plaster bagworm removal as part of general service. That is not a dodge. It reflects the fact that the attachment is mechanical rather than something a treatment can address.

What a technician will do is brush off as many accessible cases as possible during the visit, treat the perimeter and the conditions feeding the population, and reduce what comes back. On a two-story home or a heavily textured stucco wall, some cases will remain out of practical reach regardless of effort.

For a wall covered in them, pressure cleaning is what actually finishes the job. It reaches into surface texture that brushing cannot, and it removes the glue residue along with the case rather than leaving a mark behind.

How to pressure clean them off

A few practical notes, since this is the step that usually falls to the homeowner.

Start on a low pressure setting and test an inconspicuous section first. Older paint and aging stucco can be damaged by more pressure than they need.

Work top down so debris and runoff carry away from areas you have already cleaned.

Pay attention to soffits, the underside of overhangs, and the sheltered corners around windows and door frames. Those spots collect the heaviest accumulations and are easy to skip because they are not at eye level.

Do the cleaning after the population is under control rather than before. Otherwise you are repeating the job in a couple of months.

Why they showed up on your house

Plaster bagworms eat spider webs. That is the main thing to understand about them.

A house with visible bagworm accumulation almost always has spider activity feeding them, particularly in soffits, under overhangs, around exterior light fixtures, and in screened enclosures. Reducing spider activity removes the food supply, and that matters considerably more than treating the bagworms directly.

They also feed on lint, hair, and general debris, which is why sheltered areas that never get cleaned tend to support them.

Exterior lighting contributes as well. Bright white bulbs near entries draw the flying insects that draw the spiders that produce the webs the bagworms eat. Switching to warm-spectrum bulbs near doors reduces several nighttime pests at once.

What actually reduces them

Dewebbing is the highest-value step. Removing spider webs from soffits, overhangs, light fixtures, and screened enclosures cuts the food supply directly.

Perimeter treatment reduces the spider population producing those webs, which is the upstream fix rather than the visible one.

Switching exterior bulbs near entries to warm-spectrum reduces the insect traffic that starts the whole chain.

Removing the existing cases matters too, since each one represents a future adult. Brush what comes off easily and pressure clean the rest once the population is down.

Regular attention to sheltered exterior areas keeps it from rebuilding. Soffits and overhangs are the spots that get missed year after year.

When to call

A few cases on an exterior wall is normal in South Florida and not worth a service call on its own.

Dozens across multiple walls indicates enough spider activity to be worth addressing at the source, since removal alone will not hold.

Heavy accumulation in soffits and under overhangs on a two-story home is worth having someone look at, both because the access is awkward and because those areas tend to be the origin point rather than the overflow.

Seasonal homeowners returning after months away frequently find substantial buildup, along with other pests that established while the house was closed. That situation warrants a general inspection rather than just cleanup.

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