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Mealworms care while on a two week vacation

I will be going on a two week vacation soon and request ideas on how to keep my beetles/mealworms alive during that time. I guess water is the main priority, since they live in food (wheat bran).

I grow Opuntia Cactus, so can cut a pad and leave it in, but not sure how long the pad will last before going bad. Perhaps, I can stack some fresh potatoes, without cutting, on one side of their bins and hope they don't go bad.

I currently have them in bins, stacked in a dark spot. I live in Chennai, India, and the average temperature has been around 33° c (91° f) with 50-70% humidity.


  • edited October 2016

    Hi jusma, - In my system (mesh grow bags) I only make an effort to give the breeding beetles vegetable moisture & try to keep the relative humidity in the 70s. If you have your breeding stock in the same bins as the larvae then that is a different method than mine.

    In their unmanaged "wild" state they manage a life cycle without any water if temperature is not so high that they desicate. The tactic of providing moist food is, in my opinion, more to maximize their production & limit cannibalism.

    Your average temperature is not as relevant as what kind of season Chennai will be in when vacationing & the daytime temperature than. Stacked bins might also have pockets of retained warmth.

    Personally, I never liked how potatoes fared in my beetle breeding bins; I think they are too firm for being readily used by bettles. I like using radish (red outside, white inside) because they seem to be well used by beetles &, although I have only seen them after 10 days inside my beetle breeding bin, they do not appear to allow problematic mold to get growing (even though feeding beetles churn the radishes into the wheat bran). Maybe (?) the "spicy/hot" compounds in the radish has some anti-microbial properties.

    Opuntia cactus come in different varieties so I'd be curious to know what kind you have & guess it has fleshy pads. My assumption is that the open slabs of Optunia won't get grow mold even if it dries out.

    Would you tell us more about your experience using the cactus?

  • Hi gringojay. Thanks for your response. I have one bin for beetles, one for small worms and eggs, and one for the big ones. The bin on top is open, and the ones in the middles and bottom have at least two centimetres of space around all four corners for air circulation. The all measure 22in x 15in x 6in.

    If I understand you right, only the beetles need some form of moisture and would that mean my stock will not totally die without water for 10-14 days or perhaps 3-4 days after going through some radish? In reality I am only going on a vacation in December, and it will only get cooler for Winter. The temperatures I mentioned are the current average for Maximum Temperature. Although since I only have four bins at the moment, I can re-stack them in a way that there is more space for warm air to escape.

    I have a few Opuntias with thorns and it looks like the image below...

    I only tried feeding them once so far. I cut out the thorns with a scissor and split a pad in half. The worms go in through the exposed part of the pad and crawl into the pads. Some come out through where the thorns once were before being cut. I let the pads remain in my bin for a week, when it started forming a blackish colour on the external skin, and I decided to remove it for fear of rot.

  • HI jusma, - It is worth looking whether the use of Opuntia cactus has any long term effect on the mealworm larval life cycle. At this stage I am not certain if this is something that is a legitimate concern or not for your usage.

    The members of this cactus group often have anti-fungal properties in different parts of the plant & Opuntia ficus indica has one anti-fungal compound, however it is a lectin. This lectin binds to fungal chitin & is mentioned in Tables 3 & 4 of Paiva, et. al (2010) "Antimicrobial activity of secondary metabolites and lectins from plants", a FORMATEX of Brazil research report; free full text =

    More specifically Paiva, et. al in (2011) "Effect of lectins from Opuntia ficus indica cladodes and Moringa oleifera seeds on survival of Nasutitermes corniger" (termites); originally published in International Biodetermination and Biodegradation, Vol. 65 ; free full text = talks about how lectins can delay growth, interfere with pupation, etc.

    Some of the delayed development is due to lectin binding to sensillae membranes involved in chemical sensing the signals of food; plus some of the altered physiology is due to lectins binding in their mid-gut leading to the structure of gut digestive epithelium changes. The internal insect chitin, like fungal chitin, is something lectins can home in on.

    Whether mealworms could be "killed" by eating Opuntia ficus indica like the studied termites is uncertain to me. Lectins are not universal in their format & thus not all plant lectins are able to interfere with insect ester-ase (a metamorphosis & also de-toxification relevant enzyme) &/or insect phosphat-ases.

    This (2008) thesis (dissertation under Paiva & Cohelo at Pernambuco Federal University ) by G.M. de Sa Santana in Fig. 2 is a photograph of the kind of Opuntia cactus these Brazilians are studying. See " Purificacao, caracterizacao e avaliacaoa da atividade fungica de lectina de cladonia de Opuntia ficus indica"; free full text with English translation starting on pg. 27 =

    You will notice Paiva's contact & email at the time is given at end of thesis pg.23 & if you are trying to work with your local supply of Optunia in an effort to develop a Chennai project then maybe you can get some technical input from Paiva's associates. This Optunia lectin has some particular characteristics that are related to specific ions & pH; so, there may be factors you can manipulate to your advantage that you can use.

  • Again jusma, - The reason for beetles to get plant source of moisture is mainly so they don't eat the eggs for moisture. The adults will not die way before their time without moisture because carbohydrate metabolism generates water molecules internally. Possibly some of the new born larvae & eggs will dry out though.

    I breed 200 beetles in a shallow layer of bin & slice enough radish halves (washed & dried before cutting) to cover the bran surface. The radish does get a black patina but generally the beetles leave very little radish left & the skins seem to dry up for eventual removal. I think without their moisture that undetermined growth on the radish is unable to easily multiply & spread into the bran if no condensation drips onto the bran.

    Since you would be absent for a while it probably is best to leave a few cut radish to keep the beetles away from eating eggs & lots of whole radish to give them something that doesn't dry up in just a few days. Look, you are not going until December & should consider some controlled experimentation now.

    Get some radishes & put them in a container of bran that is in the same area as your mealworms. See how long the cut in half ones & the whole ones last before showing any sign of transferring contamination to the bran. Bury some inside the bran too, the feeding beetles will quickly churn them under anyway. Once satisfied you are not growing contaminants then put some beetles in with radishes & see how well they get into the whole radishes; maybe you can skip the cut open ones.

    Radish seed anti-fungal compounds have long been identified, but I don't have their specific names handy now. I have seen research that radish flesh has a compound that is converted to an anti-fungal under some circumstances. I am not able to say if this radish flesh compound transitions into an anti-fungal under conditions such as found in a breeding bin that exposes it to air & time related changes of bio-chemistry.

  • What you say does make sense. I will reserve the opuntia pads for emergencies only, and will experiment with radish in the next few maintenance activities. I may not get the same radish that you get over there, so that may also play a role. Let's see.

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