Dorsal sex pheromone glands in female Geometridae ( Lepidoptera : Geometroidea ) : a new apomorphy of the family

The female Geometridae are characterized by the presence of saccular pheromone glands. They are paired structures, invaginated anteriorly and located dorso-laterally to the rectum. The opening of dorsal saccular glands varies from wide to narrow and opens up on the 9th abdominal segment. These saccular glands are widely distributed in the family. Morphological variability of these glands can be observed. In certain species of Geometridae, the paired glands vary from short to long. Pheromone production is an established function of these glands, in the case of Rheumaptera hastata.

The Geometridae include about 21 000 described spe cies (Scoble et al., 1995), making it one of the three largest families of Lepidoptera.The taxonomy of the family has developed over a long period, but the infrafa milial classification has not received critical attention.The history of the classification of Geometridae to early in this century was chronicled by Prout (1910).Nine sub families are recognized now (Parsons et al., 1999), but the system is unsatisfactory with the monophyly of all being, at least, in some doubt (e.g.Oenochrominae sensu lato is a polyphyletic grouping) (Minet & Scoble, 1998).A ten tative classification of the Geometridae of Borneo was proposed by Holloway (1997, Fig. 2: 11).
The Geometridae are monophyletic and characterized by two apomorphies: -first, the presence of distinctive, paired tympanal organs situated at the base of the abdomen (e.g.Cook & Scoble, 1992).These structures have been reduced independently or lost (because of a few being wingless) in several Geo metridae (Sattler, 1991).-second, the larvae can be distinguished from those of other families by their "looping" progression, although "semi loopers" occur among the Noctuidae.This distinctive movement is caused by the reduction of the number of pairs of prolegs typically to two pairs on abdominal seg ments 6 and 10.A full lepidopteran complement of prolegs exists in some species (i.e., on abdominal segments 3-6 and 10), but the size of these structures tends to be reduced (e.g. in Archiearinae).In some species of Oenochrominae and Ennominae, more than the minimum number of two pairs of prolegs occur, but fewer than the full lepidopteran complement.
The present paper aims at improving the knowledge of the distribution and the morphological variability of these dorsal saccular glands within the Geometridae and to assess their possible value for phylogenetic studies.

MATERIAL AND METHODS
Dried museum specimens representing nine subfamilies of Geometridae were used to examine the internal female genitalia.The abdomens were dissected after 15 minutes maceration in hot 10% KOH and the genitalia slides were prepared by fol lowing the standard method (Robinson, 1976).The preparations were stained with chlorazol black (Carayon, 1969) and Euparal was used as the mounting medium.For the investigation of pheromone glands, the internal genitalia and segment A8 were removed; the ovipositor integument was incised midventrally and spread flat between glass slide and coverslip.I dissected 48 geometrid species from various parts of the world (mostly from Palearctic region) (Appendix 1).

DISCUSSION
In addition to both apomorphies quoted in the introduc tion, dorsal saccular glands inserted on the rectum repre sent a third autapomorphy which has been unknown until now, and characterize Geometridae as a monophyletic group.The opening of saccular glands varies from wide to narrow and opens up on the 9 th abdominal segment.It should allow the pheromone to disperse when the abdominal tip is extended.Werner (1977) provided bio assay evidence that the glands of Rheumaptera hastata produce a sex pheromone and described the morphology and histology of the sex pheromone gland of this species.The location of gland opening shows variation (see Results) and could be a character shared in some groups or subfamilies, but now it is not easy to characterise the ground plan of this trait.The opening of glands situated in mid-width of the papillae anales (Figs. 6, 7) is observed in all species examined of Geometrinae (see Appendix 1) and in certain Larentiinae (e.g.Mesoleuca albicillata, Rheumaptera subhastata (Fig. 7) and Eupi thecia linariata).This situation may be clarified, when more species have been studied.
The dorsal saccular glands are widely distributed in the family; indeed they are widespread in all subfamilies.This apomorphy can be ascribed to the ground plan of the Geometridae, with the possible exception of certain spe cies which are devoid of dorsal saccular glands.These glands have disappeared secondarily, on several occa sions, notably in some Ennominae (e.g.Abraxas grossulariata, Colotois pennaria, Gnophos furvatus, Ourapteryx sambucaria, Bupalus piniaria, Theria rupicapraria, Hylaea fasciaria and Gnophos furvatus), certain Ster rhinae (e.g.Cyclophorapunctaria and Scopula decorata) and Oenochrominae (Gastrophora henricaria).However, I tentatively interpret the absence of dorsal saccular glands in a few members of the family as a secondary loss since the dorsal glands are present in other taxa of the Ennominae (e.g.Lycia zonaria, Alcis repandata) and Sterrhinae (e.g.Rhodostrophia vibicaria, Rhodometra sacraria).Nevertheless, the absence of glands could help to clarify relationships within Sterrhinae and Ennominae.
Both the geometrid Rheumaptera hastata and some species of Arctiidae (a family that belongs to the Noctuoidea, and which is characterized by the presence of one or two dorsal saccular glands situated on the A8-A9 inter segmental membrane -see Bendib & Minet;1998 are reported to pulse the abdomen rhythmically during calling (Krasnoff & Roelofs, 1988).
It would be interesting to use histological methods which could help to establish the micromorphology of the gland.

Table 1 .
*Appendix 1. List of species examined of Geometridae.The distribution and morphological variability of dorsal sac cular glands in the family.Location of the gland opening: distal part of the rectum (dpr); subterminal part of the rectum (spr); intermediate position on the rectum (ipr); antero-medial of the papillae anales (ampa); more laterally in mid-width of the papillae anales (mwpa).