Evolution of the glow-signal system in Microphotus (Coleoptera, Lampyridae) Item Type text; Thesis-Reproduction (electronic) Authors Cicero, Joseph Michael Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 01/10/2021 11:55:43 Link to Item http://hdl.handle.net/10150/557669 EVOLUTION OF THE GLOW-SIGNAL SYSTEM IN MICROPHOTUS (COLEOPTERA, LAMPYRIDAE) by Joseph Michael Cicero A Thesis Submitted to the Faculty of the DEPARTMENT OF ENTOMOLOGY In Partial Fulfillment of the Requirements For the Degree of MASTER OF SCIENCE In the Graduate College THE UNIVERSITY OF ARIZONA 19 8 1 STATEMENT BY AUTHOR This thesis has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgement of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author. APPROVAL BY THESIS DIRECTOR This thesis has been approved.on the date shown below: so, z//y F(LbYD G. WERNER Date Professor of Entomology ACKNOWLEDGMENTS The lampyrid collections of Dr. Gayle Nelson, Dr. Frank Hasbrouck (Arizona State University) and Scott McCleve were loaned to me for examination; Vince Roth shared his personal notes and spec­ imens; Lester Lampert, Lois Hawk, and Gary Nielson reported their encounters with luminescence so that I could follow up; David Verity and Dr. James Lloyd were of tremendous help in the literature search; Dr. Floyd Werner provided me with astute guidance and advice during my study; Dr. Michael McClure and Gobi Rao assisted me with the Scanning Electron Microscope. Without the help of these friends, the progress I've made with this most difficult group of animals would not have been possible, and so it is to these people that I give my warm thanks iii TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS ......................................... v ABSTRACT ........... ................ .......... vi INTRODUCTION .................. 1 MATERIALS AND METHODS ................................... .. 4 RESULTS ........................................... .. .... 6 Microphotus pecosensis Fall 1912 ...................... 6 Microphotus dilatatus LeConte 1866 ........... 12 Microphotus LH (unidentified species) . ................ 20 DISCUSSION ................... ............ 23 REFERENCES CITED .......................... 26 iv LIST OF ILLUSTRATIONS Figure Page 1. Head of M. dilatatus, male .................. 3 2. Abdominal spiracles and microtrichia of M. pecosensis, female. 7 3. Head of M. pecosensis, f e m a l e ................ .............. 8 4. Advertising postures and their probable evolution ........... 10 5. "Abdominal twist" of M. dilatatus ? female .......... 14 6 . Palpating action of M. dilatatus ^ male . .............. 15 7. Mating pair of M. dilatatus . .......... ..................16 8. Larva of M. dilatatus . .......................... 18 9. Larval head capsule of M. dilatatus ........................... 19 10. Head of Microphotus LH (unidentified species) . ........ 22 v ABSTRACT The larviform females of M icrophotus LH (unidentified species) wander about in the leaflitter, emitting casual glows, random in their duration and interval, from light organs in the terminal abdominal sternites. Such emissions are termed "truly larviform light," in con­ trast to the uniform, continuous glow of closely related species. The nature of these emissions lends support to the hypothesis that adult light organs arose from the persistence of the larval Tight organs through the pupal stage. Females of M. pecosensis Fall assume a motionless "C" shaped posture, directing their continuous glow upward, in advertisement to their alate,. searching males. Females of M. dilatatus LeConte twist the abdomen 180°5 and wave it to accomplish the same effect. These differences are suggested to be the result of sexual selection acting upon females that display the most commanding lure. vi INTRODUCTION Green (1959) laid down the foundation for our understanding of the taxonomy of Microphotus, recognizing 7 southwestern species on the basis of male morphology, and organizing them into a workable key. The females are undescribed or inadequately described, and the literature holds no mention of the larvae. In his revision, Green mentions that the light organs of Microphotus are not apparent in the (dead) males and females. McDermott (1958) stated that presumably the Microphotus behave in a manner similar to Lampyris (see below). He (1964) described the males as being Malate and but slightly luminous,n and the females as "brachelytral, larviform, and luminous." No prior literature exists to support these statements of luminescent ability. Roth (1969) published a feature photograph of a luminescent female Microphotus, and Hogue (1974) mentioned that the female of the Pink Glowworm (M. angustus LeConte), and occasionally the male, gives off a continuous, luminescent glow. The only other mention of behavior is by Lloyd (1978, 1979), who set out a living female of the California species, M. angustus, in a Florida locality for Lampyris knulli Green to see if she would attract a contrageneric male. His attempt was thwarted when she was seized from her perch and eaten by a southern toad. The eastern United States and Old World genus Lampyris is a morphological analogue of Microphotus, and the mating behavior of 1 L . knulli and L. noctiluca L. has been described (Lloyd 1966, Dreisig 1971, 1974). The females emerge at dark and expose themselves in open areas or on perches. They glow continuously from the last 3 abdominal sternites, in advertisement to the flying males, and dim or turn off their lights and retreat into the ground when mated. This glow-find system of firefly communication is referred to as signal system I. Signal system II involves a species-specific signal from both sexes (e.g. Photinus), and it is suggested that system I is primitive, and the evolutionary precursor of system II (Lloyd 1978). My study began with the generalization that the females of Microphotus are probably all larviform, and use their luminescence to attract their alate mates, whose enormous, dragonfly-like eyes (Figure 1) facilitate their search for what amounts to mere sparks bn the ground. This, would place the genus in system I, and documentation of their habits may shed light on evolutionary considerations. 3 Figure 1. Head of M_. dilatatus , male. Line equals 1 mm. MATERIALS AND METHODS I visited localities of male specimens'of Microphotus pecosensis Fall by day, learning the foot trails, landmarks, paths of waterways and how to cross them in the dark. Areas with infrequently used roads that parallel streamsides were searched at night by driving slowly without headlights so that maximum yardage could be covered. I found no difficulty in spotting the female luminescence with peri­ pheral vision. In this way, I located 9 females at Indian Greek Campground, Prescott National Forest, Yavapai County, Arizona 60001 (1800 meters). I observed their behavior on each consecutive day of the week of June 19 to June 23, and on June 28-29, 1980, and recorded the mating protocol from observations of 6 male-female encounters. I observed 4 more females and 1 male-female encounter on June 26, 1980, at Scotia Canyon, Huachuca Mountains, Cochise County, Arizona 60001 (1800 meters) . I located a population of Microphotus dilatatus LeConte in northwest Tucson, along an ephemeral tributary of the Canada del Oro from a report by Gary Nielson, a resident of that area. I observed 7 females of this species on each consecutive day from July 23 to August 6, 1980, and recorded the mating protocol from observations of 2 male-female encounters. Four females of Microphotus LH (unidentified species) were collected by Lois Hawk of Riverside County, California, and myself at 4 Madera Canyon, Santa Rita Mountains, Santa Cruz County, Arizona 55001 (1680 meters), 19-21 May, 1980. I have assigned code letters as the species epithet since no males were found in association with them. When females were located, they were moved to the center of a beating sheet so that observations on male approach could be made. This was done very carefully and with minimum help from a flashlight to avoid disruption of natural behavior patterns. They emerge from holes or crevices, and when these retreats were found, they were marked and then later excavated for larval exuviae. Though some nights did not yield any males, the females were allowed to retreat back into their crevices and watched for the following evening. Removing and caging the females usually results in malperformance the next night, or death. Techniques for preserving the soft body of female specimens are still in the experimental stage. The larval and female head capsule is retracted deep into the prothorax when the animal is killed,