Robert E. Silberglied

Eunuchs: The Role of Apyrene Sperm in Lepidoptera?

Moths and butterflies (Lepidoptera) generally produce two types of spermatozoa: a typical nucleated (eupyrene) spermatozoon and a smaller anucleate (apyrene) spermatozoon. The apyrene sperm often predominate over the eupyrene sperm in an ejaculate and, in the female, they migrate actively to the sperm storage organ, the spermatheca. There they usually degenerate, apparently not playing any role in fertilization of the eggs. Several hypotheses for the function of the apyrene sperm have been proposed. These center around the notions that the apyrene sperm may assist the eupyrene sperm in their migration from the testes in the male to the spermatheca in the female or that they function as a nutritional supplement in the female. No experimental support for these notions has been adduced and observational evidence seems to argue against them. We propose that apyrene sperm may play, at least additionally, a role in competition between rival sperm deposited by different males. They may either eliminate, by displacement or inactivation, eupyrene sperm from previous matings or prevent or delay further mating by the female. Several peculiar attributes of the apyrene sperm support these hypotheses. Their much simplified morphology and frequent large preponderance over the eupyrene sperm, their immediate activation during ejaculation and consequent rapid migration to the spermatheca, suggest they might act to overwhelm any sperm stored there from previous matings. The same attributes would also serve to stuff the spermatheca as efficiently and completely as possible, thus perhaps signaling a successful insemination to the female and thereby reducing her receptivity to further mating. We suggest that apyrene sperm are a morphological manifestation of a more widespread phenomenon wherein accessory sperm may play an important role in sperm competition.

Ultraviolet Video-Viewing: The Television Camera as an Insect Eve

A television camtiera, like the eyes of some insects, is sensitive to ultraviolet light. When equipped with an appropriate ultraviolet-transmitting lens, such a camera can be used for the direct examtiination of ultraviolet reflectiont patterns (for example, on flowers, butterflies) that are invisible to us, but visible to inisects.

Speciation in two neotropical butterflies: extending Haldane's rule

Anartia fatima and A. amathea form a hybrid zone in Panama where F1 and back–cross hybrids are found. Crosses were carried out to determine the nature of any reproductive isolation between these two butterflies. A novel analysis demonstrated both strong assortative mating among the pure forms and an unusual example of Haldanes rule: F1 hybrid females (the heterogametic sex) from the cross A. amathea (female) multiplied by A. fatima (male) have a reduced tendency to mate. Historically, Haldanes rule has been restricted to hybrid mortality or sterility and most studies have concentrated on taxa (predominantly Drosophila) between which strong barriers to gene flow already exist. Our data suggest that Haldanes rule might be extended to cover any decrease in hybrid fitness and that mating propensity may provide a sensitive and comparable means of assessing such decreases. Other barriers to gene flow were also evident in Anartia: F1 hybrid females have reduced fertility (also a Haldane effect) and larval survivorship was greatly reduced in F2 hybrids of both sexes. These examples of hybrid disruption are expected under the dominance theory of Haldanes rule but do not exclude other explanations.

Chemistry of defensive secretions of bombardier beetles (Brachinini, Metriini, Ozaenini, Paussini)☆

Abstract Data are given on the chemical composition of the defensive secretions of species of carabids of the genera Brachinus, Stenaptinus, Metrius, Goniotropis, Pachyteles, Ozaena, and Homopterus. All produce quinonoid secretions, containing from one to three of four different benzoquinones (1,4-benzoquinone; 2-methyl-1,4-benzoquinone; 2,3-dimethyl-1,4-benzoquinone; 2-methyl-3-methoxy-1,4-benzoquinone). In most species the secretions also contain n-alkanes (tridecane, tetradecane, pentadecane).

Quinones and phenols in the defensive secretions of neotropical opilionids

Three quinones (2,3-dimethyl-1,4-benzoquinone; 2,5-dimethyl 1,4-benzoquinone; and 2,3,5-trimethyl-1,4-benzoquinone) and two phenols (2,3-dimethylphenol and 2-methyl-5-ethylphenol) were isolated from the defensive secretions of four species of opilionids (suborder Laniatores) from the Canal Zone. Phenols had not previously been reported from opilionids, and 2-methyl-5-ethylphenol was not known as a natural product. The secretions, which are mixed with regurgitated enteric fluid upon discharge, are administered by the animals by leg dabbing.

Plant Taxonomy: Ultraviolet Patterns of Flowers Visible as Fluorescent Patterns in Pressed Herbarium Specimens

Pressed flowers, in herbarium specimens, show visible fluorescent patterns matching the invisible ultraviolet patterns that the flowers show in life. The technique is taxonomically applicable since it makes an important but usually neglected floral character readily demonstrable.

Disruptive Coloration in Butterflies: Lack of Support in Anartia fatima

Experimental obliteration of high-contrast wing stripes of the neotropical butterfly Anartia fatima affected neither survival nor wing damage in a natural population over a 5-month period. There is no direct evidence supporting the hypothesis that so-called disruptive wing patterns function as protective coloration in butterflies.

Neotropical Butterflies of the Genus Anartia: Systematics, Life Histories, and General Biology (Lepidoptera: Nymphalidae)

Butterflies of the genus Anartia Hiibner are among the most common and conspicuous diurnal Lepidoptera encountered in the New World tropics. While their abundance and ease of capture have made them popular subjects for research in various aspects of lepidopteran biology, the genus has never been thoroughly reviewed or revised. Two of the authors, (R.E.S. and A.A.) have been conducting genetic, behavioral and ecological experiments on members of this genus for four years, and we feel it is both an opportunity and a necessity to condense the scattered published information with some of our own observations and results. Our experimental findings will be published separately. As treated here, Anartia consists of five species (Figure 1) in three well-defined groups (Godman and Salvin, 1882).

Inter-island transport of insects aboard ships in the Galapagos Islands.

Abstract Insects attracted to shipboard lights are regularly transported among the islands of the Galapagos archipelago. As a result, biogeographic relationships of the entomofauna are no longer subject to purely natural interpretation.

Stridulatory files as diffraction gratings in mutillid wasps

Abstract The stridulatory file present on the third visible abdominal tergite of mutillid wasps functions as a diffraction grating. Using yellow light, the mean angular rotation of the diffraction grating between orders was found to be 5·5°. This corresponds to a grating spacing of 2·9 μ, which is in good agreement with the spacing determined by scanning electron microscopy. A possible mode of formation of the stridulatory file is discussed. It is suggested that the diffraction colours that it produces may enhance the effect of the warning colours on other parts of the body.