Effects of pyrethroid and organophosphate insecticides on reared black soldier fly larvae(Hermetia illucens)

Black soldier fly larvae(Hermetia illucens)receive growing interest as a potential alternative animal feed source.These insects may be exposed to insecticide residues in the rearing substrate.This study aimed to investigate the effects of six different pyrethroid and organophosphate insecticides on this insect species'performance.The toxicity of two"model"substances for each of these classes(cypermethrin;pirimiphosmethyl)was quantified,with and without the synergist piperonyl butoxide(PBO).Critical effect doses corresponding to 10%yield(CED10)for cypermethrin(0.4 mg/kg)and pirimiphos-methyl(4.8 mg/kg)were determined.The addition of PBO to cypermethrin enhanced its relative potency with a factor 2.6.These data were compared against the relative toxicity of two analogue substances in each class(permethrin,deltamethrin;chlorpyrifosmethyl,malathion).Results suggest that exposure to concentrations complying with legal limits can cause significant reductions in yield.Exposure to multiple substances at lower concentrations resulted in negative additive and synergistic effects.Of the tested substances,deltamethrin was most toxic,causing 94%yield at 0.5 mg/kg.Analytical results suggested that transfer of tested substances to the larval biomass was substance-and concentration-specific,but appeared to be correlated to reduced yields and the presence of PBO.Transfer of organophosphates was overall low(<2%),but ranged from 8%to 75%for pyrethroids.Due to very low limits in insect biomass(~0.01 mg/kg),high transfer may result in noncompliance.It is recommended that rearing companies implement lower contractual thresholds,and that policymakers consider adjusting legally allowed maximum residue levels in insect feed.

Dietary enrichment of edible insects with omega 3 fatty acids

Edible insects are advocated as sustainable and healthy food and feed.However,commercially produced insects are often low in n‐3 fatty acids and have suboptimal n‐6/n‐3 ratios.A certain amount and proportion of these FAs is required to optimize human health.Flaxseed oil consists primarily(57%)out of alpha‐linolenic acid.An experiment was conducted to quantify the effect of flaxseed oil provision on fatty acid composition and to determine the quantity needed to attain a beneficial n‐6/n‐3 ratio.Three species were used in the experiment:house crickets(Acheta domesticus[L.]),lesser mealworms(Alphitobius diaperinus[Pfanzer])and black soldier flies(Hermetia illucens[L.]).These were provided with either a control diet or a diet enriched with 1%,2%,or 4%flaxseed oil during their larval/nymphal stage.Fatty acid profiles of diets and insects were determined via GC‐MS.The three species had distinct fatty acid profiles on all four diets,but responded similarly to flaxseed oil addition.For each percent added to the diet,the alpha‐linolenic acid content of the insects increased by 2.3%–2.7%.Four percent addition increased the n‐3 fatty acid content 10–20 fold in the three species and thereby strongly decreased n‐6/n‐3 ratios from 18–36 to 0.8–2.4.A ratio below 5 is considered optimal for human health and was achieved by 2%flaxseed oil inclusion for house crickets and lesser mealworms,and at 1%inclusion for black soldier flies.Adding a source of n‐3 fatty acids to insect diets can thus improve the nutritional quality of insects.