12/23/2020: Legend of the giant mealworm

One of the gateway drug bugs is undoubtedly the common mealworm, Tenebrio molitor. The species has been a staple of laboratories, zoos, and classrooms for over a century, functioning as an easy feeder and model organism. Despite its familiarity there is at least one myth surrounding this species… the giant mealworm. No, not superworms (Zophobas morio), but a giant common mealworm.
In his book “The Complete Guide to Rearing Darkling Beetles”, Orin McMonigle mentions the use of a giant mealworm as feeders, the origins of which are described as a trade secret among those who produce them. Old reptile forums mention the use of “giant mealworms” being the result of growth hormone added to their feed, and suggesting they were thus unsafe for reptiles in some way.
Old guard invertebrate and reptile hobbyist Kim Wismann recalls the mealworms of the olden days, which he described as meaty and nothing like the shriveled-up, desiccated, miniscule, empty tube-like excuses for living organisms often found in pet stores today. He set out to raise mealworms “the right way”, providing proper nutrition and hydration. For at least a decade he and his wife Christine also selected the largest larvae for breeding, and the end result is something straight out of the legends.
Though Kim and I disagree as to the exact reason why his mealworms grow so large (he claims it’s mostly husbandry), I did a little sub-empirical testing. I acquired a few hundred mealworms from the local pet store (packed in a nostalgic big box breeder sales cup with nutritionless wheat bran) and reared out colonies over at least 3 generations in the exact same set up on the exact same food: 16 quart plastic bins with poor quality dog food as bedding and the occasional mist or carrot/zucchini piece.
The results speak for themselves; after several generations of no selection and the same set-up Kim’s mealworms still dwarf the pet store line. I suspect the Wismann’s hard work strictly selecting the largest larvae is responsible, but no doubt providing something more nutritional than wheat bran is important to attaining some size in either line.
I will be introducing these giant mealworms on the site soon with the variety name “Wismann”, so that Kim and Christine’s legacy may live on in perpetuity with this bizarre and unique contribution to captive insect culture.

-Kyle