Introduction

Wing coupling in Tortricidae is accomplished by a bristle-like frenulum arising from the base of the hindwing that extends beneath a complementary structure, the retinaculum, a cuticular flap or group of modified scales in the basal region of the undersurface of the forewing.

In the tortricids, the male frenulum consists of a single bristle, with a conspicuously compound base and the female frenulum consists of three bristles fused at the base.

The 3-bristled condition represents the ground ancestral state. Therefore, evolution of the 2-bristled condition may either represent common ancestry or the result of convergent evolution.

In order to quantify variation in bristle number and evaluate its phylogenetic distribution, we began a survey of this character over a broad range of tortricid taxa. The current studies examines the subfamily Chlidanotinae.

Methods

Representatives of Childanotinae were obtained from National Museum of Natural History, Washington, D.C., or Instituto Nacional de Biodiversidad, Santo Domingo de Heredia, Costa Rica

Pinned adult moths were examined at 400X using a Wild M3Z dissecting microscope under transmitted light from an Intralux 6000 illuminator. The number of bristles present at the distal end of the frenulum were counted and recorded.

Results

We surveyed:

22 species in 6 genera of Hilarographini
(34% and 100% of the described species and genera, respectively)

36 species in 13 genera of Chlidanotini
(56% and 67% of the described species and genera, respectively)

68 species in 14 genera of Polyorthini
(55% and 66% of the described species and genera, respectively)

We observed two bristles in:

• 25 of the 26 species of Chlidanotini
• 13 of the 14 species of Hilarographini
• 6 of the 18 species of Polyorthini

In the distribution of the number of bristles are mapped onto a combined phylogeny of Razowski’s (1981) hypothesis of generic relationships within Polyorthini and the broadly accepted relationship among the three tribes of Chlidanotinae (i.e, Chlidanotini, Hilarographini, Polyorthini).

The predominant number of bristles observed within each genus is depicted within the parenthesis (a dash indicates that representatives of the genus were not available for examination).

Discussion

When the character states are mapped on a composite phylogeny of the subfamily, the change from 3 to 2 bristles appears to have evolved once at the base of the Chlidanotini + Hilarographini clade and; therefore, may represent an additional synapomorphy uniting the two tribes.

However, this character is considerably more variable within Polyorthini. The distribution of bristles within this tribe seems to support certain clades as previously suggested by Razowski. The presence of numerous minor deviations from this pattern putatively represent independent evolution of the 2-bristle state.

Variation in the number of bristles in the frenulum of tortricid moths may be phylogenetically informative at some levels and within some taxa, but too variable to be useful in others.

Acknowledgments

This research project was funded by a Smithsonian Women’s Committee Endowment. I thank the following: Jadranka Rota, Jon Lewis, Mary Sangrey, and my fellow interns.