With just a little help from experienced building inspectors or pest control operators given on this page we can often recognize signs of insects at a building that are not a worry, and don't need chemical or other treatment.

Here we describe and illustrate common indicators of insect activity at buildings that are generally producing harmless damage rather than damage to the structure. Those might be eggs, egg cases, the insects themselves, or their nests.

We include reader questions and photos and expert answers to give examples of both insect activity that is definitely harmless or only cosmetic as well as some examples of more-serious insect activity that need further attention.

Harmless Insect Activity vs More Serious Insect Attack

Many insects found on and around buildings are harmless or produce cosmetic damage rather than damage to the structure. We start with a very common one, bagworms.

The following reader Q&A along with photos describe various signs of insect activity at buildings and help us distinguish between harmless and harmful insect activity.

Bagworms, Insect Egg Cases Don't Cause Building Damage

Encasements of bagworm moths - Psyche caste

Based in Lincoln, MA outside of Boston, we live in a 1969 designed/built cedar sided house.In removing the original 1969 AC unit which was butted up against the exterior siding, the removal exposed a small rectangular section of original unfinished cedar that has never been finished or stained.

Wood damage was seen a short while after removing the AC but was thought to be mice damage from mice exiting the house above an entry point we screened and foamed up. However - I just noticed small bundles of thread-like material - wood? - hanging off other areas of the house.

[Click to enlarge any image]

These are few in number, widely spaced, never in any pattern or density - each seems to be a 'one-off'.

They also appear on different exposures of the house - N and E and on a separate detached garage structure- also w/ cedar vertical siding.

There is no evidence of sawdust or piles of shavings beneath any hole, no lateral damage evident and although we do have woodpeckers in the woods around us, we have not had or seen them attacking the house.

I have not found any similar images on-line so am stumped.

Any insight or suggestions as to the cause - and treatment - and who I might contact for help in the area would be appreciated. Many thanks - Michael - On 2021-01-05



Above & below: unidentified gray fibrous insect or plant material found on the exterior of buildings.

I found these things (photos above and below) all over the outside of my home and am doing some research and getting help from local pest people to identify them.

How do I evaluate insect damage to a building - is it structural or only harmless and cosmetic? - On 2021-03-13 @Michael

Reply by (mod) - insect larvae or plant seeds adhered to building exterior? Encasements of bagworm moths - Psyche caste

I'll bet a 6-pack of Castle Danger beer that if you take a couple of those plant-fibre like structures to your local county farm and home center or environmental center they can identify that item.

When I first saw these I was not sure if they were insect or plant material.

We learned they were bagworm moth eggs encased in other plant material. I think that the bagwormns particularly like short plant materials like cedar or pine needles of just the diameter and length shown in this enlargement of a Psyche caste egg case that I pulled off of a wood sided building in New York.

We've found these small woody constructions on the outside of building walls at many field inspections - identified as bagworm eggs encased in what look like individual cedar twig "leaves" or other plant material.

A number of readers have asked about these harmless egg structures. They can be removed by mechanical scrubbing, scraping, cleaning. Bagworms don't harm building structures.

These "insects" (really their eggs) do no more than cosmetic damage to wood or other exterior surfaces.

Your photos will be helpful to other readers.

Follow-up by Michael

Long delay on responding back but after putting the question out on the town list serv - several people chimed in - confirming that as you say, these funny things attached at one end and hanging down on my walls are the encasements of bagworm moths - Psyche caste.

The larvae make cocoons out of collected debris - twigs, plants, rubbish spun with silk - hence the twig or stick-like appearance.

They embed themselves only so far as the exterior stain on the cedar siding w/ no burrowing beyond the stain - although it may be my pulling the cocoon off pulls a spot of stain away however they adhere to the surface.

The initial confusion was that at passing glance they look like wood being burrowed from within.

Reply by (mod) - bagworm moth identification key

Michael

The illustration shows some examples of some of the larval cases of this genera, (Davis 1964)

@Michael, Thank you; these bagworm moth casing photos will be helpful to other readers, as these insects are ubiquitous, particularly where evergreens are nearby.

Some useful bagworm moth research:

• Kaufmann, Tohko. "Observations on the biology and behavior of the evergreen bagworm moth, Thyridopteryx ephemeraeformis (Lepidoptera: Psychidae)." Annals of the Entomological Society of America 61, no. 1 (1968): 38-44.
• Davis, Donald Ray, Diomedes A. Quintero, Roberto AT Cambra, and Annette Aiello. "Biology of a new Panamanian bagworm moth (Lepidoptera: Psychidae) with predatory larvae, and eggs individually wrapped in setal cases." Annals of the Entomological Society of America 101, no. 4 (2008): 689-702.
• Davis, Donald R. "BAGWORM MOTHS OF THE WESTERN HEMISPHERE (LEPIDOPTERA: PSYCHIDAE)." [PDF] Smithsonian Institution, Bulletin of the United States National Museum, Washington, D.C. (1964). Retrieved 2021/02/13 original source: https://repository.si.edu/bitstream/handle/10088/10074/1/USNMB_2441964_unit.pdf
  
  Introduction excerpt:
  
  This study is a preliminary revision of the tineoid family Psychidae of North and South America (including the West Indies). A treat- ment of such scope has been attempted only once (Gaede, 1936), anditwasatbestaverysuperficialstudy.
  
  Other publishedaccounts consist mostly of original descriptions, taxonomic notes, and works treating restricted areas.
  
  As a result, the interpretations of previous authors have been erroneous in several instances; furthermore, a comprehensive key for the genera and species has never been attempted; thus, reliable identification of many of these insects has been virtually impossible.
  
  The purpose of the present study is to re-evaluate the decisions of earlier workers; to complete and, where necessary, to correct their conclusions; and to investigate and utilize several taxonomic criteria in order to facilitate identification and a more comprehensive under- standing of the insects presently included in this family.
  
  The members of the family Psychidae present nmiierous problems that have greatly hindered a satisfactory treatment of the group. No single factor is unique for the family, and the close interrelation of many factors make their solution no easy task.
  
  The frequency with which many of these problems are met in the Psychidae demon- strates why this family has been considered one of the most perplexing groups, taxonomically, to be fomid in the Lepidoptera.
  

 

Investigate These Other Signs of Insect Activity

Identify small holes on joists & beams: insect activity?

I have been noticing odd holes in the truces of my home in northern NY but I am having trouble identifying the insect because I haven't seen anything crawling around. - On 2022-10-13 by Igor

Reply by InspectApedia-911 (mod)

@Igor,

In your photo I can see some normal drying splits or checking cracks in what looks like a floor joist.

I also see some extremely small black flecks, but I can't make out what they are.

And finally I think I see a cobweb with an ant trapped in it.

Take a closer look. If that ant is the insect that you are seeing, or if you are seeing sawdust or frass appearing under or on or near the wood framing, you may have a carpenter ant infestation.

Is it Rot or Insect Damage?

I have this rot in the sophets of my home, how can I tell what caused this and should I be worried about the structure of my home. - On 2021-12-15 by Austin

Reply by Inspectapedia Com Moderator - soffit damage can be due to leaks and inadequate ventilation but this looks like insect activity

@Austin,

First let's notice that there are horizontal holes along the wood grain of this fascia board on your home's soffit. While rot may be present too, these are insect damage holes.

There appears to be some sawdust-like material in some of those "gouges" along the wood grain. I can't see enough detail in your photo to know if this is carpenter ant frass (soft, all wood) or remains of termite activity (a mixture of mud and wood) but you may be able to determine that by a closer look and a bit of probing.

This damage is enough that you should get an inspection from a licensed pest control operator (PCO) to determine if the insects are active and need treatment.

Separately we need to assess the extent of damage to the structure. If it's only in the soffit fascia board I'd simply replace it. If rafter tails or rafter bodies are damaged, more repair may be needed.

Separtely, you want to inspect your roof for leaks especially at the eaves, and it's evident that you have no roof ventilation installed.

So it's also worth inspecting in your attic for signs of leaks into the attic and for the extent of moisture and mold that might be in that area.

 

Bird or Spider Droppings vs Holes in Wood

Hi. Got a bad problem at my house. We had been figuring it was something in the paint maybe ftom 5 years ago but now I’ve found the same thing occurring in the eucalyptus wood glider on our screened porch.

These minuscule holes with a minuscule white drip beneath them are in the millions all over our cedar shakes house and now in a totally different wood on the glider. Terminix treats for wolf spiders and they can’t figure it out. - On 2021-03-28 by Claudia

On 2021-03-29 by danjoefriedman (mod)

@Claudia, I don't have a size scale in your photo so I can't be sure but It looks to me like spider poop and very small insect holes that could be characteristic of old powder post beetles damage.

But I don't normally find powder post beetles invading building exterior siding or trim; more-likely those insects bore into sills and main beams or occasionally floor joists.

Compare what you're seeing

with POWDER POST BEETLES

and inspect further in your basement or crawl space to see if there are any signs of insect activity there.

Mud or Concrete on Wood Framing Isn't Insect Activity

We live in Southeastern Wisconsin - Does anyone know what might be causing this damage to the rafter in my basement? - On 2021-03-08 by Patty

Reply by (mod) - mud and mold on interior wood structure: previous exposure to weather?

@Patty, I see what looks like mud, thick on the sides of joists and on subflooring, with some straight edges marked in the mudas if the material was left outdoors and exposed to weather.

On the edge of some of the blocking I see what could also be a bit of fungal growth - fine black growth patterns on the edges of the doubled blocking and joists.

Sometimes we see similar material on wood framing that was used first in a concrete form, then re-used in construction. But the presence of muddy brown material on both the sides of blocking and the edges of joists and on the surface of plywood all look like mud. Yet I don't see water or flooding marks on the materials.

 

Is it Sap or Insect Damage

What caused this? - On 2020-02-17 by Steve

Reply by (mod) - insect damaged siding or fencing? Sap?

Steve

That's certainly interesting.

It looks like old insect damage; I can't say if the white material is sap or insect frass. The pattern and location is not characteristic of termites, but it'd be useful to poke at or pick out a bit of the white material to examine its consistency.

What I want to know is if the material is comprised of

- sawdust
- sap
- larvae
- old paint
- something else

it would also help to know

- country and city location
- type of wood (species)
- how long that wood (fencing) has been in place
- whether the wood was salvaged from some prior use

 

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2023-11-25 by Amanda - little white things on my trees and tomato plants

I don't know if you can maybe help me with this. I found small little white things on the frame of my tomato plant and it was also on some leaves.

Im not sure if its termites (because there was a cluster of these on the one side of the wood frame) or if its worm eggs, or what type of insects.

I had to cut half of my tomato leaves that got infected with this coz the leaves started to look sickly and dying.

On 2023-11-25 by InspectApedia Publisher

@Amanda,

Those look like larvae emerging from a nest between two logs. Too blurry to identify the species with confidence. But possibly a type of insect-scale such as Cottony Camilla scale or Cape Myrtle bark scale. They don't look fuzzy enough to be mealy bugs or wooly aphids.

Bottom line probably a type of grub or larvae.

They are not termites. You wouldn't see termites out on open surfaces like that.

...

Continue reading at CARPENTER ANTS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see INSECT INFESTATION / DAMAGE - questions & replies posted originally on this page.

Or see these

Recommended Articles

• INSECT INFESTATION / DAMAGE - home
• BEDBUG PESTS
• CARPENTER ANTS
• CARPENTER BEES
• FLIES, MOSQUITOES REMOVE or REPEL
• INSECT DAMAGE PREVENTION
• INSECT DAMAGE - WOOD REPAIR STEPS
• INSECTS & FOAM INSULATION
• MERULIPORIA FUNGUS DAMAGE
• MOLD: A COMPLETE GUIDE TO MOLD
• MOTHS, MOTHBALL ODORS
• PESTICIDE EXPOSURE HAZARDS
• POWDER POST BEETLES
• TERMITE INSPECTION & DAMAGE ASSESSMENT

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