Is a butterfly pupae male or female...how to tell

[Dave McCormick]

Having 81 large white pupae in my bedroom (ones I reared from caterpillars) made me think ofwondering how to find out which ones would be male or female. Looking around and at various texts, I found the way.

When you have caterpillars, you don't always know what sex it will turn into (mostly you don't until it hatches from pupae) but most people wait until this stage to find out (this is one of my large white pupae, close to hatching a female):

Large White PUpae (Female)

Now there is a way to tell if the pupae is male or female (in moths I don't think its the same) . If you look close enough at a butterfly pupae you can make out some features of the adult, the wings, eye mark and possibly proboscus. Now to find the sex, you'll need a good eye (magnifying glass or get a good close up photo).

This is your pupae (with area circled that I am talking about)

LW Pupae

Here is the area up close:

Bottom of Pupae

This area can determain the sex of the butterfly. This area corrosponds with the anal claspers of the adult. A male pupae has two tiny bumps close to the tail of the pupae (which is in shot) and in female, these are usually slimmer and lighter. So if your able to work out this, you can sex your pupae prior to hatching. In some butterfly pupae you can see which might be female or male, just by looking at it, but for most, a closer inspection like this can tell you.

[Cotswold Cockney]

Yes, I've used a similar technique in the past with a x6 hand lens, a x10 is even better. I had a small illustrated article published on the technique in the Amateur Entomologists' Bulletin about thirty years ago.

If you look at the terminal four ventral abdominal segments on the pupa, in the male they are all clear bands. However, with female pupae, there is a clear central slit in one of those four terminal segments which IIRC, houses the Bursa Copulatrix (BC) ... where in adult butterflies, the male inserts the spermataphore.

With many Nymphalid butterflies and a number of other species, you can tell if a female has been fertilised by looking at the BC. After successful mating, there is often a short (2-3mm) trace of the spermataphore present in the female's BC. This is useful for the butterfly breeder to confirm successful pairings.

I have sometimes been present when say Apatura iris (Purple Emperor) separate after copulation in my breeding cages. Sometimes that trace of spermataphore will stretch for two-three inches as the pair separate so that for a second or two before it breaks, the pair are still connected by a fine silk like thread. PE pairings usually last for 90-120 minutes. Less than that can mean an unsuccessful pairing. Provided they are allowed sufficient time to become sexually mature ( partly why males invariably emerge about a week before females ) a 'good' male PE can be paired with up to three virgin females provided it is allowed to recover for a few days between each pairing with correct feeding. In captivity, both sexes can live for well over a month and still be active. I suspect the same is true in the wild.

Small pupe such as most Lycaenids can be very difficult to 'sex' this way because of their smaller size and the fact the the terminal segments are far less clearly defined. Hawk Moth pupae can be 'sexed' with the naked eye checkinh those four terminal segments ~ well, it was possible for me years ago without glasses but, the old minces are not what they used to be...