Mealworm / Superworm frass air particulate sizes

Does anyone know the air particulate sizes for mealworm/superworm frass and chitin? I'm wanting to ensure the air filter I am using is successfully stopping the farm dust.

I have an exhaust system setup to exchange the air.


  • A magnified picture of mealworm frass can be seen in Fig.5.3 (page 62 of pdf, pg. 53 of original) of B. Sprang's thesis (2013) "Insects as food: assessing the food conversion efficiency of the mealworm ...." Note the variable sizes; picture has a measure bar & clearly marks the 1.4mm long × 0.1 mm wide piece.

    Larvae produce different size frass depending on both their instar life stage and particular diet (also pathogen load). There is some specific data on different instars' frass for some caterpillars (larvae of moths) in forestry research.

    In general terms mealworm larvae grow up to about 30 mm, but the caterpillars I'll describe bellow grow up to about 50mm. So if you want to use the following data to extrapolate to mealworm larvae you need to do a bit of math & also take into acvount that the relative change in frass length for each instar is probably not linear.

    Malacosoma neustrium caterpillar fed leaves from different varieties of the same kind of tree produced frass when 1st instar = 0.25 - 0.3 mm long frass; when 2nd instar = 0.34 - 0.67 mm long frass; when 3rd instar = 0.69 - 0.97 mm long frass; when 4th instar = 1.37 - 1.77 mm long frass; & when 5th instar = 2.01 - 3.6 mm long frass. ( The other caterpillar Aniosota peiglieri also grows to 50 mm; it's 5th instar produces frass 3.24 - 3.42 mm long, but it's 1st instar's frass is about twice the length of M. neustrium's.)

    Thus if we try to simply extrapolate from this larvae (caterpillar) that grows to 50 mm over to the mealworm that grows to only 30 mm a basic adustment by a conversion factor of 0.6 (30 ÷ 50) seems a potential starting point. This is to say that possibly 1st instar mealworms produce frass as small as 0.15 mm long (0.25 mm of M. neustrium x 0.6). And 5th instar nealworms produce frass as large as 2.16 mm long (3.6 mm of M. neustrium x 0.6). I'll leave it to others to assess these extrapolations using Sprang's magnified image of frass, which I assume was collected from a mixed age colony.

  • Are those small particles airborne? Going with the smallest instar in your example, would 0.25 - 0.3 mm be in the air?

  • edited April 1

    In my opinion only if or when substrate containing frass is manipulated (poured, sifted, shaken, rotated, etc.). Just being excreted & crawled amongst by larvae I see no reason frass would become notably airborne. By the way 0.25 mm long frass is not 1st instar mealworm larvae. That is M. neustrium data & I've extrapolated 1st instar mealworm larvae might be only 0.15 mm long.

    An exception seems to be rearing larvae in TinyFarm mesh net grow bags, since frass "falls" through the holes & until settles underneath the grow bag frass is in air. I use these mesh bags & can generate a lot of frass drifting out by pushing around on the underside with an implement (wood dowel), which gets "dustier" the more vigorously underside of grow bag is manipulated.

    n my lax temperature/humidity controlled larval set-up sometimes moving more of the frass (than larval churning alone results in falling through the mesh) encourages instar progression; frass compound farsenol slows larval instars (sorry lost old German link). Lots of frass farsenol in a sense signals colony survival rate is adequate, so slow down population replacement drive & relieve pressure on food resource exploitation.

Sign In or Register to comment.