Further to my previous post here “Sexing Pupae2”, dated 9th July 2013, I would now like to follow up this original message with an accurate method for sexing 5th instar Apaturinae larvae. Please see the comparative images below:
Consistent with the larvae of some other species of Lepidoptera, such as Laspeyresia caryana , Plodia interpunctellla  certain members of the Ephestia and even Pieris rapae  to name but a few, the developing testes of male Apaturinae specimens can clearly be seen through the integument of their 5th abdominal segment. Visualization of the developing testes usually becomes very apparent 8-10days post ecdysis into their 5th (and final) larval stage and continues to develop through to pupation. The photograph of the male specimen (above) was taken one day prior to generation of his silk pupation pad. Confirmation of the image details was provided by Ivar Hasenfuß, co-author of chaprter 5 of "Handbuch der Zoologie / Handbook of Zoology (Handbuch Der Zoologie/Handbook of Zoology, Volume IV : Arthropoda : Insecta)", who upon seeing the images is quoted as writing “the patches are in the sites of the anlagen of the testes (which are close below the integument) and are certainly due to the pigmentation of the testes”. Further confirmation of the specimen sex(es) has also been obtained via examination of the subsequent pupae produced and comparison against known sex determining features. See previous “Sexing Pupae2” post, dated 9th July 2013.
What is interesting to note about the development of the testes in the Apaturinae larval specimens however, is that unlike other specimens documented to date where the developing testes are dark (black/purple/red) in colour, those of the Apaturinae appear to be very pale, almost white? Hasenfuß suspects that this observed difference in colouration is “a marginal effect of the metabolic processes. This view is in accordance with its rearness and the differing colors may indicate a different chemical nature of the pigments (malanine, pterine or other)”.
I trust that some of you will find this observation of interest.
 Tedders etal, 1967, "Male and Female Reproductive Systems of Laspeyresia caryana, the Hickory Shuckworm Moth (Lepidoptera: Olethreutidae)", Annals of the Entomological Society of America, Vol.60(1), pp280-282/3.
 Kishan Rao Sambaraju, 2003, “Studies on Factors Affecting Behavior, Ecology, and Reproductive Success of Indianmeal Moth, Plodia interpunctella (Huber) (Lepidoptera: Pyralidae)”.
 Stehr, 2011, Immature Insects.