The text below is grayed out because it is not intended to be read. It is a necessarily imperfect OCR of the original and is only used by a search engine.
Volume 34, Number 2
261
Boston, p. 1212; Priestaf 1972, J. Lepid. Soc. 26: 104) may reflect the relatively recent introduction of P. rapae to North America and its subsequent geographic overlap with native Pieris (Scudder 1889, loc. cit.; Klots 1951, loc. cit). The possibility that crosses between P. virginiensis and P. n. oleracea from this locality are fertile can be tested using laboratory-reared stock. Bowden (in litt. and 1972, Proc. Brit. Entomol. Nat. Hist. Soc. 4: 103-117) found that some crosses between virginiensis and napi oleracea individuals (from stocks from different localities) produced viable hybrid offspring (tests of hybrid fertility were negative but too few to be conclusive); others produced infertile eggs. If the artificial crosses produce fertile hybrid offspring, then one might expect to find some evidence of introgression in sympatric populations (cf. Hovanitz 1963, J. Res. Lepid. 1: 124-134). If the crosses are not fertile, then the observation that these two distinct, sympatric, native Pieris do not exhibit more effective pre-zygotic isolating mechanisms is curious (cf. Shapiro 1975, Am. Midi. Nat. 93: 424-433).
Frances S. Chew, Department of Biology, Tufts University, Medford, Massachusetts 02155.
Journal of the Lepidopterists' Society 34(2), 1980, 261-262
UTILIZATION OF GRASS INFLORESCENCES AS ADULT RESOURCES BY RHOPALOCERA
Adult Lepidoptera utilize a number of energy sources to supplement the nutritive material assimilated during the larval stage. While flower nectar is the most common adult resource, others, e.g., rotting fruit, carrion and dung are often utilized (Downes 1973, J. Lepid. Soc. 27: 89-99; Neck 1977, J. Res. Lepid. 16: 147-154). Flowers most frequently visited are those with colorful petals and/or sepals. While tropical grasses are visited by a large number of insect species (Soderstrom & Calderon 1971, Biotropica 3: 1-16), as a general rule, grasses have non-conspicuous, anemophilous flowers which have few, if any, insect visitors.
Herein I report massive utilization of grass inflorescences by several species of Rho-palocera. Observations were made along Sandy Creek in Enchanted Rock State Park, Llano Co., Texas, on 27 October 1978 from 1000 to 1700 h. Skies were cloudless; temperature range was 10°-25°C during the observation period.
Rhopalocera were visiting inflorescences of two grass species: K-R bluestem, Both-riochloa ischmaeum (L.) Keng var. songarica (Fisch & Mey.) Celarier and Harlan, and Dallis grass, Paspalum dilatatum Poir. The following species and numbers were observed during a single transect: Precis coenia (Hiibner) (51), Danaus gilippus strigosus (Bates) (8) and Cynthia cardui (L.) (2). Butterflies had their probosces extended towards and around the base of achenes of the inflorescences. Achenes of both these grass species were post-anthesis, but some substance was apparently being removed from the shiny surface of the achenes.
Other rhopaloceran species present at this site but not observed at the grass inflorescences were Anaea andria Scudder, Ancyloxypha numitor (Fabricius), Atlides hal-esus corcorani Gunder, Chlosyne lacinia var. adjutrix (Scudder), Colias (Zerene) cae-sonia Stoll, Colias eurytheme Boisduval, Eurema nicippe (Cramer), Nathalis iole Boisduval, Physiodes phaon Edwards and Phyciodes vesta Edwards. Most of these species flew over the two grasses with no evidence of attraction. Butterfly families represented by the above species include Hesperiidae, Lycaesidae, Nymphalidae and
262
Journal of the LEPIDOPTERISTS, Society
Pieridae. These butterfly species visited a number of flowering plants, e.g., Eupatorium havanense H.B.K. (Compositae), at which no Precis, Danaus or Cynthia were observed.
The grass-visiting species ignored not only various other flowering plants but also a number of other grass species, e.g., side-oats gramma, Bouteloua curtipendula (Michx.) Torr., most of which was brown with achenes fully desiccated. The stage of desiccation, i.e. maturation of seed, is the apparent key factor in restricting butterflies to the two species of grass. Both the grass species visited by Rhopalocera are weedy, drought-resistant, naturalized grasses which have extended seed production compared to native grasses (pers. obs.). B. ischmaeum also grows in nearly monospecific meadows on interstream high areas and terraces. A few butterflies visited inflorescences in these areas, but their numbers were not comparable to the lower sites. While arborescent vegetation at these higher sites may have restricted butterfly access, some butterflies were present; the probable reason for reduced utilization was low soil moisture which caused more rapid achene maturation. The observation of three Precis in immediate proximity to each other on one particularly "green" Paspalum inflorescence supports this idea.
Of interest is the identity of the substance obtained by Precis, Danaus and Cynthia from the surface of the achene of Bothriochloa and Paspalum. Lepidopteran adults have long been known to feed at sap exudates and honeydew on leaves (Norris 1936, Trans. R. Entomol. Soc. Lond. 85: 61-90). Karr (1976, Biotropica 8: 284-285) reported unidentified moths feeding at a "nectar-like material" of a grass species in the Canal Zone (Panama); a later report (Pohl et al. 1979, Biotropica 11: 42) indicated this substance may have involved nectar-like production by an ergot. However, I have observed several species running probosces over the surface of apparently healthy leaves without honeydew deposits or fungal infestation. Obviously, some exuded substance on the leaf or achene surface has some attractive (and presumed nutritive) value to a number of adult Rhopalocera. Grass species with extra-floral nectaries are unknown (Pohl et al., op. cit). One wonders whether the substance(s) involved are secondary compounds produced to deter herbivory (see Levin 1976, Annu. Rev. Ecol. & Syst. 7: 121-159). However, water-soluble compounds, e.g., sugars and amino acids, are normally not present on such external surfaces. Water-insoluble compounds, e.g., waxes, flavonoid phenolic compounds and terpenoids, often occur on these external surfaces. These compounds are not nutritive in nature, however; normally they serve as feeding and/ or ovipositional deterrents or attractants. At this point one does not know whether these butterflies were obtaining a nutritive substance or were merely being stimulated by surface phytochemicals.
Raymond W. Neck, Pesquezo Museum of Natural History, 6803 Esther, Austin, Texas, 78752.
Editors' Note:
We express our gratitude to all who have given of their time and expertise to make this Memorial Issue possible. Especially, we sincerely thank Lee D. and Jacqueline Y. Miller (Allyn Museum of Entomology, 3701 Bay Shore Drive, Sarasota, Florida 33580), who together solicited and initially screened most of the articles; Robert K. Robbins (Smithsonian Tropical Research Institute, Box 2072, Balboa, Republic of Panama) for editorial assistance; and the contributors themselves, many of whom knew Harry Clench personally. The frontispiece photograph was provided by Kenelm W. Philip (Institute of Arctic Biology, University of Alaska, Fairbanks, Alaska 99701).
Those wishing to obtain reprints of single papers should address requests to individual authors; those wishing to obtain reprint of the entire issue should address requests to the Carnegie Museum of Natural History, 4400 Forbes Avenue, Pittsburgh, Pennsylvania 15213.
Date of Issue (Vol. 34, No. 2): 23 September 1980