Archon, , Bryk, 1934

Matsumoto, Kazuma & Orr, Albert G., 2021, The occurrence of a sphragis and genital modification in Hypermnestra, Archon and Sericinus (Lepidoptera: Papilionoidea: Papilionidae), Journal of Natural History 55 (15 - 16), pp. 1033-1057 : 1051-1053

Archon

In Archon , the male secretory material is plastered onto the female genital plate without specific form, but it is entirely external. Moreover, male scales are attached laterally, regularly arranged on either side. Hence, the sphragides of the two Archon species can be regarded as true sphragides. The male scales very likely make the terminal segments of a mated female’s abdomen difficult to grasp, as well as providing strength to the sphragis at its edges, which are normally the place where other males begin trying to gain access in other species.

There are somewhat similar characters in the sphragis and male and female genitalia among the genera of Luehdorfiini and Zerynthiini. The structure of the sphragides of Archon species are similar in basic design to those of Allancastria species which were considered to be true sphragides by Matsumoto et al. (2018) in that the male secretion is spread over the female genital plate and male scales are attached. These features may suggest an ancestral form of the sphragis, if the tribes Luehdorfiini and Zerynthiini have a common sphragis-bearing ancestor. The sphragides of Bhutanitis and Zerynthia are thought to be vestigial ( Matsumoto et al. 2018) with male scales no longer methodically used and the amount of secretory material much reduced. The use of scales from the male valvae in Archon is comparable to Luehdorfia , although in this genus the scales are bonded into the sphragis.

A relatively flat female genital plate is also found in Luehdorfia , as well as Zerynthia , Allancastria and Bhutanitis (Zerynthiini) , and these are all considered to be plug rejecting genital structures ( Matsumoto 1987; Orr 1988, 1995; Carvalho et al. 2017; Matsumoto et al. 2018). In Archon , the ductus bursae is lacking and the spermatophore has at most a short thin stalk which would not provide a good anchor for the sphragis. The ductus bursae is also very short in Zerynthia and numerous Acraea species ( Orr 1988) . The female genital plates of Archon species are elevated behind the ostium, which necessitates more secretory material to effectively cover that region. Most Archon sphragides examined did not do so; rather the spread of the sphragidal material ended at the front of the raised area, i.e. just behind the ostium. This curtailing of the sphragis, possibly in response to the structure of the genital plate, seemingly reduces its effectiveness in deterring access by the male to the ostium. The genital plates bear some similarity to those of Bhutanitis but in other Luehdorfiini or Zerynthiini an obvious ductus bursae (long and sclerotised in Bhutanitis ) is normally found.

In Zerynthia and Allancastria , a sharp, hooked uncus and/or valvae occur and these are believed to be used for sphragis removal ( Orr 1995; Matsumoto et al. 2018). We suppose the hooked uncus has a similar function in Archon species and suggest this is implied by the extent of interspecific variation in these structures. It is noteworthy that the uncus of male Luehdorfia is well developed and hooked and the male uses it to lever up the foliate sphragis (Matsumoto unpublished). The aedeagus is thin but long, strong and sharppointed both in Archon and Luehdorfia . A thin sharp-pointed aedeagus may be used for working under the sphragis and into the ductus bursae in Luehdorfia . It must be long in Luehdorfia , because the ductus bursae in this genus is long, and sclerotisation of the wall of the ductus in this genus suggest that this type of rough, angled aedeagus insertion often occurs and females are exposed to the risk of injury from the ductus (the same explanation may apply to the relationship between the long sharp-pointed aedeagus and long sclerotised ductus bursae in Bhutanitis ; Matsumoto et al. 2018). But it is unclear why the aedeagus of Archon must be so long, unless the length is needed to remove the sphragis. It is however possible the loss of the ductus is both a way of avoiding injury as well as making it more difficult to secure the sphragis.

It is also unclear why the frequency of sphragis-bearing females is so low in Archon , especially in A. apollinus . One possible reason for this is that the males of Archon species might produce limited sphragidal material. In many female specimens without sphragis, the long black scales besides the genital plate were lost; probably due to disturbance by mated males that did not leave a sphragis. It is also possible that males are very good at removing the sphragis, as in the sphragis-bearing satyrine species Heteronympha penelope , in which female genitalia are unmodified from the form found in the non-sphragisbearing species of the genus, while male genitalia are highly modified ( Orr 2002). In this species it is normal for a male to produce a large elaborate sphragis on his first mating, but the low incidence of intact sphragides in wild populations and in museum collections suggests that the sphragis is often removed by second or third males, as was observed in caged populations ( Orr 2002).

The museum specimens of Archon are mostly in ‘good’ condition without physical damage, hence are probably virgins, bred in captivity ( Carvalho et al. 2017; Matsumoto et al. 2018). In the present study, we tried to exclude apparently laboratory bred specimens, but we cannot exclude the possibility of inclusion of some non-wild specimens in our data and this could be one reason for the low frequency of occurrence of the sphragis in Archon apollinus . However, some medium-old females apparently caught in the field a week or so after the eclosion did not bear a sphragis, and the seven out of 13 dissected females without sphragis had a spermatophore, indicating that the males do not always form a sphragis when mating, or that the sphragis had fallen off or been removed. Perhaps, like H. penelope ( Orr 2002) males can form one or two sound sphragides on their early matings but are also very good at removing the sphragides of other males, resulting in misleadingly low counts.

For Archon species , it would be desirable to examine the frequencies of sphragis and spermatophore in a good number of field-collected specimens, as well as observing mating by fresh males with virgin females in captivity. And as in Hypermnestra , information on all aspects of reproductive biology from both laboratory and field studies is to be desired.