Showing papers in "American Midland Naturalist in 1959"

Notes on the Ecology of Slugs: Arion circumscriptus, Deroceras reticulatum, and D. Iaeve

Abstract: have treated species that also occur in North America (Barnes and Weil, 1944, 1945; Dainton, 1954). The few papers from North America have dealt primarily with the economic aspects of slugs (Lovett and Black, 1920; Karlin and Naegele, 1958) or with some particular phase of their biology such as feeding habits (Ingram and Peterson, 1947). In the course of field studies of a small mammal population near Ann Arbor, Michigan, three species of slugs, Arion circumscriptus Johnson, Deroceras reticulatum (Muller), and D. laeve (Muller) were found together. 'Two of these forms (A. circumscriptus and D. reticulatum) have been introduced from Europe, while D. laeve is native to North America. D. reticulatum is now well established as one of the more abundant slugs in North America. A. circumscriptus is recorded in many localities from New York to California (Pilsbry, 1948). Its distribution is quite local, however, and it is found apparently only around areas of human habitation (or from near refuse dumps, campsites, and the like). D. reticulatum and A. circumscriptus are unrelated, but native to the same region; D. reticulatum and D. laeve are closely related, but originated in different regions. This relationship seemed to present an ideal situation for a comparative study of some aspects of their ecology. Of special interest is the relative importance of taxonomic affinity and region of origin as related to some of the ecological factors. A number of field observations were obtained which seemed to indicate several differences in their ecology. Laboratory experiments were then designed to test the validity of these observations. The studies reported here are preliminary. The experiments were simple and less comprehensive than desirable, but for the most part they give the desired data and a few general conclusions can be drawn from them. More intensive investigations in both field and laboratory are needed to determine the significance of some of the results. Differences in activity patterns (seasonal as well as responses to shorter weather variations) and habitat preferences were observed. The ecological factors which appeared most important in explaining some of these observations were temperature, moisture, and food preferences. Experiments were conducted to determine the importance of these factors. A few experiments were also conducted to investigate toleration of 485

Population Control in Guppies

Abstract: Populations of aquatic organisms appear to be self-limiting (Rose, 1957, 1959, 1960). Breder and Coates (1932) have shown for the guppy, Lebistes reticulatus, that 5.5-liter aquaria would support 9 adult fish. This was their final number whether they started with one or 50. Once nine had become adult, even though more were born, no more could survive to adulthood. Apparently young guppies grew up only as replacements for older ones that died. Shoemaker (1944) repeating the observations found that a steady state is reached but that in time the numbers drop off from the plateau. After two years a new cycle of population growth began. Breder and Coates believed, but did not demonstrate, that population was controlled only by infanticide. The data presented in the present paper indicate that both the production and survival of guppies decrease as numbers of adults increase.

A Contribution on the Life History of the Collared Peccary in Arizona

Abstract: The collared peccary, Pecari tajacu sonoriensis (Mearns) is a common inhabitant of central and southeastern Arizona. It is found from about 2,000 feet above sea level in the Sonoran desert of southeastern Arizona to an altitude of over 6,500 feet above sea level in the higher ranges (Knipe, 1957). Between September, 1955 and January, 1957, I conducted research on the techniques of trapping, tagging, and transplanting the collared peccary. While carrying out this research work miscellaneous information on the life history of the collared peccary was obtained. Study area.-Most of the field work was conducted in the Tucson Mountains, located about six miles west of Tucson in Pima County, Arizona. Elevations range from about 2,200 feet above sea level at the lower elevations to 4,677 feet above sea level on Wasson Peak, the highest point in the Tucson range. The terrain is rugged in the higher elevations around 3,000 feet above sea level with numerous rocky outcrops scattered throughout the higher peaks. Below the foothills, the terrain levels out into sandy plains. Climatic conditions in the study area consist of high temperature, high evaporation, and low annual rainfall. The greater part of the annual precipitation usually comes as summer thunderstorms which are of short duration. The winter rains, unlike the sudden summer downpours, may last several hours with a slow-soaking precipitation that percolates into the soil and is retained (U. S. Dept. of Agriculture, 1941). The study area lies wholly within the Sonoran Desert (Shreve, 1951). The principle feature of this area is the great variety of cacti which grow in association with the creosote-bush (Larrea tridentata), bur-sage (Franseria deltoidea), mesquite (Prosopis juliflora), palo verde (Cercidium microphyllum), and ironwood (Olneya tesota). Saguaro (Carnegiea gigantea) is abundant throughout most of the area and in places forms dense stands. Cholla and prickly pear (Opuntia sp.) are less striking but even more abundant than saguaro. The hedgehog cactus (Echinocereus sp.), barrel cactus (Ferocactus Wislizeni), and fishhook cactus (Mammillaria sp.) are

Observations on the Nesting Behavior of Digger Wasps of the Genus Ammophila

Abstract: In the course of studies on the behavior of various digger wasps, I have from time to time made a few notes on various species of Ammophila (tribe Ammophilini of the subfamily Sphecinae, family Sphecidae). My reasons for publishing these rather fragmentary notes at this time are two. First, I have been much impressed by the variation in nesting behavior which occurs in this genus, both interspecifically and intraspecifically, suggesting that an intensive comparative study of these wasps might yield important results in the field of the evolution of behavior. Second, I would like to re-examine the idea that wasps of this genus sometimes "use a tool" to assist them in closing their nests. The Peckhams (1898) first reported this behavior in Ammophila urnaria and considered it an act of intelligence. Many subsequent writers have not hesitated to cite this behavior as

An Analysis of the Feeding Habits of Rana p. pretiosa in Yellowstone Park, Wyoming

Abstract: Knowledge of the food and feeding habits of the western spotted frog has been primarily based on the reports of Tanner (1931), Fitch (1936), Schonberger (1945) and Moore and Strickland (1955). These analyses have all been purely qualitative in nature and based on collections made at one time during the spring or summer. The following study is based on an analysis of the contents of the digestive tracts of 178 individuals collected from populations in Yellowstone Park, Wyoming, during 1953, 1954, and 1955. Thirtyfive of these frogs were collected on August 17, 1953, about one-half mile northeast of Fishing Bridge along a backwater of the Yellowstone River. The remainder of the sample was collected in 1954 and 1955 from other populations near the north end of Yellowstone Lake. Because the sample represents all age groups and was collected gradually over the course of several seasons it has been possible to learn something of seasonal variation (both qualitative and quantitative) in the diet of the western spotted frog. Acknowledgment.-The writer wishes to acknowledge the role of members of the United States National Park Service in Yellowstone National Park, Wyoming, without whose cooperation this study could not have been carried out. Collection of materials was in accordance with a Class B permit. Appreciation is also expressed for use of facilities of the Museum of Vertebrate Zoology, and the Department of Zoology, University of California. In connection with the identification of materials recovered from the guts of frogs the writer wishes to gratefully acknowledge the assistance of the following persons: Dr. Paul D. Hurd, Jr., Assistant Entomologist, Department of Entomology and Parasitology, University of California, identified dipterans, hymenopterans, lepidopterans, and orthopterans (as well as certain representatives of other smaller groups); Hugh Leech of the California Academy of Science, identified both adult and larval beetles and certain other larvae,; Dr. Willis Gertsch of the American Museum of Natural History identified the spiders; Dr. Robert Usinger, Department of Entomology and Parasitology, University of California, and John Herring identified the hemipterans; Dr. Donald Denning of Velsicol Corporation identified the trichopterans; Dr. Edward L. Bousfield identified the amphipods; Ernest Roscoe identified the snails; and Helen Sharsmith of the University of California Herbarium identified certain plant remains. Finally, it is a pleasure to acknowledge the assistance and direction of Dr. Robert C. Stebbins in the preparation of this manuscript.

The Forest-Prairie Ecotone in Northeastern Illinois'

Abstract: This paper describes the vegetation of pre-settlement times in Kane County, Illinois, and discusses its composition and pattern of distribution as shown by the General Land Office Survey notes. The "pre-settlement vegetation," or the plant cover which prevailed prior to human modification by settlement, is a strong influence on the land settlement and land use pattern of an area. Kane County is situated in northeastern Illinois about 30 miles west of Lake Michigan and 25 miles south of the Wisconsin border. The county contains 513 square miles and the topography is modified by the irregular deposition of glacial material. A prominent morainal system bounds the Fox River, the main drainage system of the county, creating a narrow, but prominent, valley (Fig. 1). The remainder is, for the most part, gently rolling and well-adapted to farming, although the northern half of the county is hillier and more dissected by ravines than the southern part. Rainfall in the region averages 34 inches a year and the mean annual temperature is about 480F. (U.S.D.A., 1941). The county is located at the edge of Transeau's (1935) 'Prairie Peninsula' in the transition region between the prairie and forest, and it is because of this ecotonal position that the area was chosen for study.

Moisture Regulation in Mound Nests of the Ant, Formica ulkei Emery'

Abstract: and sometimes reared is a widespread habit found not only among the social insects but also in certain birds, alligators, beaver and muskrat. It is a reasonable assumption that not only protection from predators but also a regulated or modified microclimate regime results from this habit. This has, in fact, been satisfactorily demonstrated for the Australian Mallee-Fowl (Lewis, 1940; Firth, 1956) and for termite mounds (Holdaway and Gay, 1948). The situation in ant mounds is less clear, and in this paper an attempt is made to determine if the construction of a mound nest by one species of moundbuilding ant results in a regulated microclimate with respect to the moisture content of the mound, and if so, whether a relationship exists between the moisture content of the mound and the moisture preferendum of the inhabitants. This specific question is pertinent to the broader ecological problem of how animals cope with the fluctuations in the external physical environment. Mound nests are, of course, not the only habitats in which the activity of the organism modifies the microclimate of its surroundings. To a limited extent most organisms, simply by their metabolic activity, probably alter their environment. But this ability appears marked only in a few habitats-such as the hives of honey bees, the carton nests of certain wasps and the honeycombs of the wax moth Galleria melonella L. (Allee et al., 1949). A unique case is the modified microclimate achieved by certain Army ants of the genus Eciton in which the brood shelter, or bivouac, is formed entirely of the linked bodies of living ants (Schneirla, Brown and Brown, 1954). The microclimate within ant mounds has been measured by a large number of investigators working in several different countries. Most of their papers report data on temperature relationships, while a few deal with the carbon dioxide content of ant nests. This literature has been reviewed by Raignier (1948). Since Raignier's review two pa

Observations of Reptiles and Amphibians in a Louisiana Swamp

Abstract: Few studies have been made of the reptiles and amphibians of a swamp. Two of these are the studies of Wright (1932) in the Okefinokee swamp of Georgia and a population study of Thamnophis sauritus proximus by Tinkle (1957) in Louisiana. This report contains a summary of observations and experiments made with several species in a cypress-gum swamp near New Orleans in 1953 and 1954. The study was conducted on the Tulane University Sarpy Wildlife Refuge in St. Charles parish. The habitat has been described in detail by Tinkle (op. cit.), including a report regarding vegetational changes and fluctuations in water level. Most of these data were obtained on 31 visits to the study area between November, 1953, and December, 1954 and were sometimes incidental to the population study of the western ribbon snake referred to above. The water in the swamp is shallow (1-3 feet) except in borrow-pits traversing the refuge. There are open areas in the swamp resulting from timbering or representing abandoned oil well drilling sites. In these open areas cattail (Typha domingensis) and cutgrass (Zizaniopsis milliacea) predominate with pickerel weed (Pontederia cordata) in the shallow areas and water hyacinth (Eichornia crassipes) in the ditches. The swamp proper contains cypress (Taxodium distichum) and gum (Nyssa aquatica) with some ash (Fraxinus sp.) in the drier areas. Thickets of palmetto (Sabal minor) occur throughout the swamp. The dominant plants on the many ridges traversing the swamp are willow (Salix nigra), maple (Acer drummondii) and groundsel tree (Baccharis halimifolia) with blackberry (Rubus sp.) in the more open and disturbed areas. Many parts of the swamp were investigated, but most observations were made along a ridge, 25 feet in width and 600 yards in length. At the end of this ridge was an abandoned wellsite consisting of open water, cypress swamp, and marsh flats, several ridges and deep ditches. This site was divided into 90 quadrats with aluminum tape, each quadrat 15 feet square. This area will henceforth be referred to as the study area and the ridge leading to it as the main ridge. On each visit to the refuge notes were kept on the numbers of each species seen. On certain days attempts were made to survey and compare several areas within the swamp, to investigate in greater detail specific microhabitats, and to look for hibernating and egg-laying sites. The marking work was restricted to the study area although marked animals were searched for outside the quadrated area. All

Distri6ution, Habitat, and A6undance of the Topeka Shiner Notropis topeka (Gilbert) in Kansas

Abstract: Notropis topeka (Gilbert) occurs from "Minnesota and South Dakota south through Iowa, Nebraska, Kansas, and Missouri" (Moore, 1957:134). Compared with distributions of other plains fishes, this range is small. No other fish has a similar area of distribution. In Kansas, N. topeka has been reported from scattered localities that indicate its presence throughout the northern part of the state (Kansas River Basin) and in part of the Arkansas River Basin in south-central Kansas (Fig. 1). Approximately 37 localities are represented, 10 of which are west of 970 longitude. Nine of the 10 western records were obtained between 1882 and 1887 when the first general surveys of fishes were made in Kansas (Gilbert, 1885:98, 1886:210, 1889:39; Cragin, 1885:108; Evermann and Fordice, 1886: 185; Hay, 1888:245, 248, 251, 252 [as Notropis aeneolus Hay], 246). The tenth record is a single specimen (KU 3108) obtained by A. B. Leonard and A. B. Williams from Cherry Creek, Cheyenne County, in April, 1947. Other recent collections west of 970 longitude have not included Topeka shiners. Breukelman (1940a) failed to find them in extensive surveys of streams in northwestern Kansas, and in 1958, Cross and B. C. Nelson did not find N. topeka at any of 30 western localities, including all those cited by Gilbert, Cragin, and Hay. In the Kansas River Basin east of 970 longitude, N. topeka was reported from three localities between 1882 and 1887 (Gilbert, 1884 [types from Shunganunga Creek, Shawnee County, described as Cliola (Hybopsis) topeka], 1886:210; Graham, 1885:73). Graham's record may be erroneous, because it evidently was based on the same collection from the Missouri River that was reported by Jordan and Meek (1886:12-14), who did not list the Topeka shiner from that locality. Breukelman (1940b: 380), reporting on fish in the University of Kansas Museum of Natural History, tabulated 27 specimens from the "Kansas [river], and tributaries not otherwise named." Presumably, this record refers to specimens collected by the State Biological Survey in 1912, from Rock Creek, Douglas County. Jennings (1942: 365) listed N. topeka from two localities, one of which is the only record from the Marais des Cygnes System (Missouri River Drainage). Minckley (1956:353-354) reported one additional locality in the Kansas Basin. The species is now known from many other streams in the eastern part of the basin, mostly in the Flint Hills Region. All of the older records from the Arkansas River System are west of 970 longitude, except for two specimens (formerly Indiana Uni-

Some Studies on Crayfish Distribution in a Small Pond

Abstract: While trapping crayfish of the species Orconectes virilis Hagen (formerly Cambarus virilis Hagen; Hobbs, 1942) during the summer of 1956 in a small pond in Lincoln, Massachusetts, it was noted that certain sites within the pond yielded more crayfish than others. Also it was noted that the catches varied from time to time throughout the summer. These observations prompted speculations about the preference of the crayfish for certain sites in the pond, possible migration, and their population density. Therefore, it was decided to plan the trapping activities for the summer of 1957 to include a study of some of these problems. METHOD The site of the study was an overflow basin of the Hobbs Brook Reservoir in Lincoln, Massachusetts. Physically the basin approximates a rectangle about 180 m long in the east-west direction and about 45 m wide in the north-south direction. The average depth of the water is about 1.5 m when filled. The water level fell from about 0.5 m below normal level at the beginning to about 0.9 m below normal by the end of the experiments. The east and west ends are lined with large rocks which normally extend under the surface of the water. The sides are lined with gravel, the bottom of the soutlh side being muddy in comparison to the somewhat more sandy bottom of the north side. Three stations were used in the studies. Station A was located in the middle of the east end (Fig. 1). Station B was located on the north side about 38 m west of the east end. Station C was similarly located on the south side, directly across from Station B. Crayfish were trapped, marked, and released at these three stations. Minnow traps baited with fish trimmings were used to trap the crayfish. Haddock heads seemed to be the most effective bait. Salmon and haddock backs were less effective and mackerel - heads least of all. The traps were placed approximately 7 to 8 m off shore at each station within a radius of about 2 m. Four experiments were carried out (TABLE I). In Experiment I the animals were trapped at Station A and released at Stations B and C. In Experiment II the

Phytosociology of the Lowland Forests of Northern Wisconsin

Abstract: land forests. The composition and floristic relationships of the upland forests have been described by Brown and Curtis (1952). The present study is concerned with the second type, with the forests which are found on poorly drained sites which receive runoff waters from adjacent uplands or which are subjected in other ways to temporary or permanent high levels of soil moisture. Such sites are a prominent feature of the heavily glaciated terrain in northern Wisconsin. They are found in partially filled lake basins, along stream terraces, or on flat lands of glacio-lacustrine origin. They support forests which vary from stands of pure conifers in the wettest situations to stands of nearly pure hardwoods on the most mesic sites.- The substrate in these lowland forests is rich in organic matter, frequently in the form of peat which may be present in beds many feet in thickness. The climate of the area is the Type I of Bochert (1950); it is characterized by cold snowy winters, reliable summer rains, and low rates of evaporation. The snow cover is usually deep enough to protect the soils from frost penetration to any great depth and often prevents any freezing of the soil. Cold air drainage into the lowland forest basins serves to increase the severity of the temperature microclimate and may result in frost on any day of the year. The importance of these lowland forests is greater than their areal extent might indicate. Perhaps less than 10 percent of the land area in northern Wisconsin is occupied by them, but they have received far less disturbance than any of the upland types. Their direct economic potential as sources of lumber or other forest products is low, but they are of great importance in stabilizing the water supply of the region. Their role in providing wintering grounds for the white-tailed deer is also of high significance in the over-all conservation program (Christensen, 1954).

Studies on the Alaskan Blackfish Dallia pectoralis I. Habitat, Size and Stomach Analyses

Abstract: The end-product of evolution via mutation and natural selection frequently results in the establishment of a species well adapted to a limited environment. The distribution of the Alaskan blackfish, Dallia pectoralis Bean, limited to arctic and sub-arctic fresh waters, (Jordan and Everman, 1896; Wilimovsky, 1954), suggests that because of modifications necessary for survival in the cold, this species may have become over-specialized, resulting in an organism suitably adapted to the cold. We successfully maintained 50 live blackfish under refrigeration in the laboratory at Catholic University during 1953 and 1954. A second group of 30 animals was kept at room temperature (250C). The members of this group died within a few weeks even though we attempted to gradually acclimatize them to room temperature. Other factors suggest that this species is well adapted for survival in the cold. For example, Turner (1886) reports that the Alaskan blackfish was frequently collected by natives, stored in grass baskets, frozen, and fed to dogs. Upon being rewarmed, it is reported, the fish was regurgitated alive by the dogs. Such reports are part of Alaskan folk-lore. Scholander et. al. (1953) in an attempt to verify such reports performed critical metabolic and survival studies on the blackfish, the results of which indicated that the fish is, indeed, coldadapted but it cannot survive freezing. The above studies suggested to us that an ecological and physiological investigation of the blackfish was warranted. The physiological study will be published separately. The ecological study included determinations of the total alkalinity, pH, dissolved oxygen and temperature of the environment, and of the total length, weight, and stomach contents of the fish. All these factors are interrelated; the physical environment influences the occurrence of food as well as the distribution of the blackfish.

Taxonomic Studies on the Hydras of North America. VII. Description of Chlorohydra hadleyi, new species, with a Key to the North American Species of Hydras

Abstract: identical merely on the basis of the presence of zoochlorellae, although a few workers on hydra taxonomy questioned this procedure. European specimens were first named Hydra viridissima by Pallas (1766), which name has priority over Hydra viridis (Linnaeus, 1767). Marshall (1882) described a form from brackish water, Hydra viridis bakeri, characterized by a maximum column length of 1.5 mm for budding individuals, and tentacles half the length of the column. He mentioned several "races" of green hydra and called attention to the great discrepancies in size and proportions of green hydras described by earlier workers (Rosel, Pallas, Kastner, and Schiffer). Schiffer had reported a green hydra with a column length of 1 1/2 inches (37.5 mm), and had observed a small long-tentacled form and a large shorttentacled form, with up to 20 tentacles. Schulze (1917) figured the embryonic theca and testis of European Chlorohydra viridissima (placed by him in a separate genus), and suggested that there might be miore than one species of green hydra in Europe. This partial description by Schulze, with a few additional comments and a figure of the holotrichous isorhiza in a later paper (Schulze, 1927), until recently constituted the principal characterization of Chlorohydra viridissieta available for taxonomic purposes. Hyman (1929) called attention to the lack of a complete description of the common green hydra of Europe, and to the resulting uncertainty that all green hydras throughout the world are conspecific. The necessary information about the European green hydra has now been supplied by the beautifully illustrated article by Brien and Reniers-Decoen (1950), 440

A Quantitative Study of Mountain Beaver Activity

Abstract: Most of the articles on the habits of mountain beavers [Aplodontia rufa (Rafinesque 1817)] describe the animal as being chiefly nocturnal. Grinnell and Storer (1924) refer to it as "reclusive" and as one whose, "activity is confined to night time." Bailey (1936) and Seton (1929) similarly allude to the nocturnal activity and the last writer states, "he seems positively to dread the sunshine." In the Pacific Northwest, Scheffer (1929) believes the animal to be active in its burrows during the day time but that it never leaves the burrows except at night. More recently, however, Dalquest (1948) finds that although the mountain beaver is principally active at night, it is frequently seen during the day, especially in the fall. Because all of these published statements, except those of Dalquest (op. cit.) were at variance or inconsistent with this author's own field experience with the mountain beaver, the following observations and experiments were planned to investigate the nature of its activity.

Flight Activities of Two Species of Ants of the Genus Formica

Abstract: This paper is a description of flight activities of Formica obscuripes Forel and Formica ulkei Emery which occurred on the Edwin S. George Reserve, Livingston County, Michigan. Although each species has been studied rather extensively, there have been no previously published records of nuptial flights. On the contrary, each has been suspected of having no true flights, or of having flights which are very limited in extent (Weber, 1935 and Holmquist, 1928).

Algae in Colorado Soils

Abstract: The algae are important constituents of the living, changing complex that we call the soil. Soil contains not only minute mineral fragments but also water, gases, dead plant materials, insect larvae, nematodes, protozoa, bacteria, fungi and algae. This is an intricate association and the algae have a part in it. They add organilc matter to the soil, influence chemical changes therein, are known to fix nitrogen and are a food source for small animal life in the soil. Several workers throughout the world have listed the various algaethey have found in the soil (Bristol-Roach, 1927; Fritsch, 1922; Fritsch and Salisbury, 1915; Russell, 1923) and a few have studied the activities of these micro-organisms (Bristol, 1920; Petersen, 1935; Skinner, 1932). Most of these studies were made in Europe. In this country as early as 1912, W. W. Robbins examined 22 soils and found 12 species of algae living in them. Later, G. T. Moore and associates (1919; 1926) listed 31 species of algae found existing in soils at the Missouri Botanical Gardens, some of them rather deep below the surface. In 1925, Bonar and Goldsmith made a study of desert soils in the Southwest and found that such soils contained a total of 14 genera of algae; no specific list was published. Lowe and Moyse (1934) listed 27 species of algae from soils of Manitoba, Canada. The limited information on soil algae in this country suggests a need for further inventory, especially in the intermountain West. It is the purpose of the following paper to list such algae as have been found in Colorado soils, with brief mention of the conditions of their habitat.

A Study of the Dynamics of a Population of Peromyscus gossypinus and P. nuttalli Subjected to the Effects of X-Irradiation

Abstract: A large number of experiments have been conducted in recent years that have demonstrated the deleterious effects of ionizing radiation in both individuals and in populations. It is a well established fact that if radiation is delivered to the gonads, inheritable changes will occur in the germ cells. The net effect of these changes is to increase the genetic variability of a Mendelian population, if the irradiated individuals are allowed to breed with other individuals in the population. The present paper is a report of the effects of x-irradiation on a natural population of two species of wild mice; the cotton mouse (Peromyscus gossypinus) and the golden mouse (Peromyscus nuttalli). Studies on the dynamics of any natural population are important because the individuals that make up such a population are the basic units by which gene exchange is effected (Blair, 1953). It is generally recognized and accepted that any population of sexually reproducing organisms represents a gene pool from which the various combinations of genes that are best suited to a particular environment are chosen through the process of natural selection. The present study was designed to analyze the effects of a presumed increase in genetic variation in mouse populations which were already well adapted to the environment in which they were living. It was expected that, in this case, the effects of x-irradiation would be revealed by a study of the dynamics of the two species populations as well as in the customary more easily measured morphological form. This work was made possible by a grant from the U. S. Atomic

Experimental and Natural Hybridization between Bufo terrestris and Bufo fowleri

Abstract: In analysing populations in which interspecific hybridization is suspected, the systematist seeks out the similarities and dissimilarities between the parental species. The alleged hybrids are then evaluated in terms of the differential characters of the two species. Determining which and how many of the character differences are to be selected as criteria of hybridization constitutes the critical phase of the procedure. Two species may differ so widely that individuals of one group are readily separable from the other. The differences may relate to the presence or absence of several qualitative characters. Some of the quantitative characters may display no or little overlapping of values when the measurements are plotted. In this case, a "hybrid index" method (Anderson, 1936, 1949; Hubbs and Hubbs, 1943) may be employed and it may be safely inferred that individuals with intermediate values represent products of hybridization. In other cases, the differences between two species may be such that there is considerable overlap when the values for any single character are plotted. Bufo terrestris and Bufo fowleri are two such entities. Few of the morphological differences between them are absolute, in the sense that one species possesses a characteristic that the other entirely lacks. A unique morphological feature of B. terrestris is the knob-like swellings on the posterior ends of the interorbital cranial crests. For the most part, however, the differences between B. terrestris and B. fowleri are ones of degrees. The two toad species differ in the size and distribution of warts, the extent of ventral spotting, the shape and coloration of the parotoid glands, the configuration of the snout, and other variable quantitative traits. These characters overlap broadly. The paucity of well-defined morphological differentials between the two species renders difficult the detection of hybridization in sympatric areas. Convincing data requires the demonstration that experimental hybrids between the two species resemble individuals collected in mixed breeding aggregations. The data reported herein deal with the success attained in reconstructing experimentally the suspected natural hybridization between B. terrestris and B. fowleri in southeastern Louisiana and adjacent Mississippi. Controlled cross-breeding experiments revealed the morphological features of hybrid individuals, as well as provided the

Seasonal Biotic Events in Two Colorado Alpine Tundra Ponds

Abstract: The rugged terrain and the rigorous climatic conditions of the alpine tundra present a rather formidable picture to the field biologist. The long winter, deep snow, blizzards, and high winds make the alpine tundra relatively inaccessible for biological studies with ordinary equipment during much of the year. Even in the short summer, high winds, frequent cold showers, and summer blizzards are likely to. occur at any time. It has long been generally recognized that such severe climatic conditions are remarkably restrictive upon the aquatic as well as the terrestrial biota of the tundra. With the exception of Neldner and Pennak (1955), who conducted a full open season study on a single Colorado alpine pond, the American literature on tundra ponds is almost non-existent, being limited to brief descriptions, single visits, and casual observations. European investigators, such as Brink and Wingstrand (1949), Pesta (1933, 1935, 1943, 1948), Pichler (1939a, 1939b), Stirnimann (1926), Thomasson (1951, 1952), and Turnowsky (1946), have produced a much more extensive array of literature, but like the majority of American papers, these are brief descriptions and not full seasonal studies. It is the purpose of the present paper to give a limnological description of two small Colorado alpine tundra ponds, based upon observations and data gathered at relatively frequent intervals during the entire open season. Some routine physical and chemical determinations were conducted, but special emphasis was placed upon the ecology of the benthic fauna and zooplankton, with little regard to the botanical aspect. Acknowledgment. -I am especially indebted to Dr. Robert W. Pennak for the confirmation of many taxonomic determinations and criticism of the manuscript. I am also grateful to Mr. H. B. Herririgton for species determination of fingernail clam specimens. I am further indebted to Mr. Robert P. Higgins for assistance in the field determination of pond morphometry.

New Termites from Venezuela, with Keys and a List of the Described Venezuelan Species

Abstract: Early in 1956 Dr. Francisco Fernandez-Yepez of the Universidad Central de Venezuela, Facultad de Agricultura, Maracay, Estado Aragua, kindly sent me a collection of eight species of termites. These were collected in various Venezuelan states from 1949 to 1955, mostly by him. Among them were two undescribed species. In June, 1956, Dr. Fernandez-Yepez sent an additional 13 species of termites, 7 of which he collected on a trip in the spring of 1956 to Venezuelan Guiana, Mt. Auyantepui, and 6 species from North Central Venezuela. Mt. Auyantepui is the site of Sir Arthur Conan Doyle's science-fiction, "The Lost World," an isolated, raised plateau on which (elsewhere) extinct prehistoric monsters still survived (1912). One new species was found in the material from Mt. Auyantepui. I visited Venezuela in November and December, 1955 and found that Heterotermes damaged growing sugar cane, Nasutitermes cacao trees. Heterotermes and Nasutitermes were also the subterranean termites most injurious to buildings and material stored in them, while Cryptotermes was the dry-wood termite causing most damage to wooden furniture and the woodwork of buildings. Species of Syntermes harvest grass in the daytime; nests are underground. No soldier occurs in Anoplotermes, species of which may damage the roots of crops. The discovery of the above-mentioned three new species brings the total number of termite species so far recorded from Venezuela to twenty-eight. A list and key to the known forms are appended below. Doubtless many other species occur in this large country with its varied climate.