Protophormia Terraenovae (Northern Blowfly)
Storage, Maintenance & Dispensing Guide
Taxonomy
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Kingdom: Animalia (Animals)
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Phylum: Arthropoda (Arthropods)
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Class: Insecta (Insects)
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Order: Diptera (Flies)
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Family: Calliphoridae (Blowflies)
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Genus: Protophormia
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Species: terraenovae​
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Northern Blowflies are one of the most versatile feeder insects available for mantises, jumping spiders, assassin bugs, and other insectivorous invertebrates.
They can be purchased as either larvae (maggots) or pupae, depending on how and when you intend to use them.
Before ordering, it is important to understand the difference between larvae and pupae, as each serves a different purpose.
Understanding the Life Cycle
Larvae (Maggots)
Larvae are the active feeding stage that hatches from the egg.
They are cream-coloured, soft-bodied, and constantly moving.
Larvae may be:
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Fed directly to your animals
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Allowed to pupate naturally
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Refrigerated to delay development
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At room temperature, larvae will gradually develop into pupae and eventually emerge as adult flies.
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Pupae
Pupae are the inactive stage between larva and adult fly.​
They appear as dark brown oval capsules and do not feed or move. Inside the pupal casing, the larva transforms into an adult fly.
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Pupae are purchased for the purpose of producing adult flies and are not intended to be fed as larvae.
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Adult Flies
Adult flies emerge from pupae and are excellent feeders for mantises, jumping spiders, and many other predatory invertebrates.
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Their movement stimulates a strong feeding response and encourages natural hunting behaviour.
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Which Should I Buy?
Choose Larvae If:
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You want the longest possible storage life.
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You would like the option of feeding larvae directly.
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You want greater control over when pupation occurs.
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You are unsure how quickly you will use them.
Choose Pupae If:
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You intend to feed adult flies only.
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You want flies to begin emerging soon after arrival.
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You prefer a simpler feeder option.
If you are uncertain which life stage best suits your needs, feel free to contact me before ordering.
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How Much Should I Feed?
The amount fed depends on the species, size, sex, and condition of the animal.
As a general guideline:
Jumping Spiders
Adult Regal Jumping Spiders (Phidippus regius) typically consume:
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Females: 2–3 flies per feeding, twice per week
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Males: 2–3 flies per feeding, once per week
Juveniles generally require fewer feeders and may be fed smaller flies or larvae.
Mantises
Small mantis nymphs often consume a single larva or fly per feeding.
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Larger nymphs, subadults, and adults may consume multiple larvae or flies in a single feeding session.
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Always adjust feeding based on abdomen size and the overall condition of the animal.
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How Many Should I Order?
This is the most common question I receive.
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Many new keepers purchase more feeders than they can reasonably use before age begins to affect quality.
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Northern Blowflies are sold in increments of 25.
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25 Count
Suitable for:
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One or two jumping spiders
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A small mantis collection
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Customers trying blowflies for the first time
50–100 Count
Suitable for:
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Several spiders or mantises
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Most hobby keepers
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125–250 Count
Suitable for:
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Larger collections
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Breeders maintaining multiple animals
500+ Count
Typically purchased only by breeders or keepers maintaining substantial collections.​
If you are unsure how many to order, please contact me before purchasing. I am happy to recommend a quantity based on your collection and feeding schedule.
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Shelf Life and Freshness
The storage times below are general guidelines.
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The age of the stock when purchased plays a significant role in how long it will remain viable. Older stock naturally has a shorter remaining shelf life than freshly received stock.
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If long-term storage is important for your project, please contact me before ordering and I can advise on the age of the current stock.
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Larvae
When refrigerated at 1–3°C (34–37°F), larvae generally remain viable for up to six weeks.
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Most customers will begin to observe a gradual decline in performance after approximately five weeks.
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Pupae
When refrigerated at 1–3°C (34–37°F), pupae generally remain viable for up to three weeks.
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After three weeks, emergence rates decline rapidly.
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Storage
Important
Always use a ventilated container. When insects are refrigerated in a sealed container, condensation forms inside the container.
Excess moisture can:
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Weaken or kill larvae
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Reduce pupal hatch rates
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Encourage mould growth
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Shorten the lifespan of adult flies
Keeping the contents dry is one of the most important aspects of successful storage.
Larvae
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Store refrigerated at 1–3°C (34–37°F).
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Refrigeration slows development and delays pupation.
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Keep the substrate dry and well ventilated.
Pupae
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Store refrigerated at 1–3°C (34–37°F).
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Refrigeration slows development and delays adult emergence.
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Keep pupae dry and well ventilated.
Adult Flies
Adult flies may be stored refrigerated at 1–3°C (34–37°F) to keep them inactive between feedings.
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Every 3–4 days:
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Remove flies from refrigeration for 1–2 hours.
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Provide a food source such as fruit or a small smear of honey on damp paper towel.
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Return them to refrigeration afterward.
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Dispensing Feeders
Larvae
Remove the desired number and place them directly into the enclosure.
Uneaten larvae may burrow into substrate and pupate.
Pupae
Place pupae into a ventilated emergence container at room temperature and allow them to hatch naturally.
Adult Flies
The easiest method of feeding adult flies is to use refrigeration to temporarily immobilize them.
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For best results:
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Prepare several small feeding cups.
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Place only enough flies in each cup for a single feeding session.
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Refrigerate the cups.
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Remove only the cup currently being used.
Cold-stunned flies recover quickly once warmed. Using multiple small feeding cups greatly reduces escapes and makes feeding much easier.
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Odour
Northern Blowflies are commercially raised on fish-based substrates and naturally possess a noticeable odour.
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Keeping them refrigerated significantly reduces smell.
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If necessary, the original sawdust may be replaced with fresh untreated hardwood sawdust to further reduce odour.
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Can They Be Cultured?
Technically yes. ​Practically speaking, most hobbyists choose not to.
Blowflies naturally develop on carrion, manure, and decomposing organic material. Commercial production typically utilizes fish-based substrates.​
For most keepers, purchasing larvae or pupae as needed is far easier and considerably more pleasant than maintaining a breeding colony.​​​​​​
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