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This paper describes the embryonic development of Lytta viridana from oviposition to the formation of the blastema. The egg has the features commonly found in an insect egg. Bilateral symmetry is shown by the shape of the egg, variation in thickness of the vitelline membrane, and distribution of the yolk components. In the newly laid egg the vitelline membrane is porous. This is believed to be the first record of this phenomenon in insects. During cell division chromatin elimination occurs along the spindle to the equatorial plane. It is especially marked in the first meiotic division, but continues into late cleavage. During the first 4 hours the periplasm flows first forward to the cephalic region and then caudad along the central axis. The belief is expressed that this movement is associated with the prefusion movements of the sperm and fertilization. Fertilization occurs at about 3 hours. During the first 14 hours of development, marked morphogenetic movements of the deutoplasm occur.

The somatic chromosome complements of nine sarcophagid species are described using methods presented in the first paper of this series. These species are Acridiophaga aculeata, Kellymyia kellyi, Protodexia australis, P. hunteri, Pseudosarcophaga affinis, Sarcophaga aldrichi, S. cooleyi, Sarcophaga "H", and S. reversa. P. affinis has 19 or 20 chromosomes whereas all the others have 12-chromosome complements most of which can be distinguished.

This paper describes the use of the serological procedure known as the precipitin test to study the rate of digestion of host blood in mosquitoes. In the laboratory, at constant temperatures, precipitin reactions were obtained on blood meals of Aedes aegypti eight days after engorgement when the mosquitoes were held at 11 °C. but only one or two days after engorgement when the holding temperature was 27 °C. Field studies with A. hexodontus in northern Manitoba also showed that temperature has a strong influence on the rate of blood digestion. Pertinent literature is reviewed and the limitations of the precipitin test are discussed. Until now little attention has been devoted in Canada to possible disease transmission by mosquitoes. Increasing interest in mosquitoes as vectors of the encephalitides and proved transmission of western equine encephalitis by Culex restuans in Manitoba suggest the importance of further knowledge of mosquito physiology.

The fat component of guinea pig milk has been analyzed by gas liquid partition chromatography. Nine of the fatty acids present in butterfat were not detected in guinea pig milk fat. Paper electrophoretic analysis of the guinea ig milk casein showed that it contained a-casein (25.3%) and p-casein (48.1%! Previous work on the isoantigenicity and autoantigenicity of guinea pig milk (2) showed that this milk does not cross-react with cow milk under the conditions of the experiment which were employed. This observation has stimulated interest in the constitution of the protein components of guinea pig mill

This paper records a discovery of basic, partially independent nuclear units that lie within a common nuclear membrane of some vertebrate cells. The cells concerned are found in series from small (1–2 μ) to large (10–15 μ or more). The smallest cells possess one basic nuclear unit, the larger cells have several. The series of cells from small to large represent stages of a life cycle. Certain of the basic nuclear units act as reproductive organelles and certain large cells are parent cells producing new small cells thus closing one life cycle and starting another. The large cells are formed from the small cells through a series of fusions. The basic nuclear units behave similarly to micronuclei, the reproductive organelles in ciliates, but the fusions of the vertebrate cells are permanent, not temporary unions such as conjugation in ciliates.

The various tissues of two species of insects, one cold-hardy and the other not, were found to have melting points between −0.5° and −1.0° C. Because of this uniformity, the relationship between temperature and extent of ice formation, quantitatively worked out for blood of Loxoslege sliclicalis (L.) in a previous paper, may be considered representative of insect tissues in general, except possibly those of insects that withstand freezing.

Kieffer's genus Lasiohelea is now recognized as an association of subgenera of Forcipomyia having in common an elongated second radial cell in the wing. Tokunaga separated two of the component subgenera of this Lasiohelea complex, using adult characters. The present paper introduces the evidence of the early stages, adding six new species to the subgenus Lasiohelea, four to Neoforcipomyia, and one to Warmkea.

In lake chub, Couesius plumbeus, hypophysectomy causes marked regression in the testes, suppresses the mitotic ability of the spermatogonia, completely blocks their transformation into spermatocytes, and affects the normal secretory activity of the lobule boundary cells. Spermatogenesis is largely reinitiated and secretory activity of lobule boundary cells is restored by injections of a partially purified salmon pituitary extract, by mammalian luteinizing hormone, and by crude extracts of whole pituitary of salmon. The gonadotropin responsible for testicular maturation is similar to mammalian luteinizing hormone; a factor like mammalian follicle-stimulating hormone is probably not physiologically active in this fish. Although gonadotropin is primarily responsible for gonadal maturation, other factors such as thyrotropin and somatotropin probably have a stimulatory effect by acting synergistically with the gonadotropin. The paper presents details of a technique for hypophysectomy.

Samples of nine crystalline mustard oil glucosides including sinigrin were isolated from plant tissues of species in the families Cruciferae and Tropaeolaceae. The isolations were achieved by the use of column chromatography on neutral alumina, cellulose powder, activated carbon; by paper and thin-layer chromatography; and by crystallization from methanol–water mixtures.Feeding responses of fifth instar larvae of Plutella maculipennis (Curtis) were tested on agar–cellulose diets containing individual glucosides at various concentrations in the presence or absence of 0.1 M glucose. The amount of feeding was measured by counts of frass pellets produced by the larvae during the test period. All the above-mentioned glucosides were found to act as feeding stimulants for the larvae of P. maculipennis. However, the relative palatability of these glucosides at the same concentration (20 mg per 10 ml of water in the diet) was found to be in the following order: progoitrin > glucocheirolin = glucoconringiin = glucoerucin > glucotropaeolin = sinigrin = sinalbin > gluconasturtiin = gluconapin. Higher concentrations of the glucosides, gluconasturtiin, and gluconapin were toxic to the larvae.

The study of the microstructure of the shells of sessile barnacles shows that in many of them there is a figure, or pattern, that is constant in both recent and fossil shells of the same species and this can be used in identification.It is quite easy to find the pattern in the shell and the method of doing it is fully described in this paper.

Sixty-three valid species of freshwater triclads (Platyhelminthes, Turbellaria), representing 16 genera, are listed from North and South America. Comments on nomenclatural problems or changes of taxonomic status are included when necessary. Worldwide distributional data are provided at the generic level, but at the specific level only the Western hemisphere is considered. The taxonomic status of four incompletely described species is also briefly discussed. A bibliography of 84 references directs users of the checklist to the most important recent papers dealing with the taxonomy and distribution of the individual species, and provides a key to the older literature. New records for Canada, involving nine species, are given preliminary mention.

Trichodina elizabethae n. sp. (which is commonly hyperparasitized by the suctorian Endosphaera engelmanni Entz), T. galyae n. sp., and T. domerguei (Wallengren) saintjohnsi n. subsp. are described from Newfoundland waters; the first two from the radiated shanny and lumpfish respectively, and the last from the mailed sculpin, lumpfish, and shorthorn sculpin. T. jarmilae n. sp. parasitizes the sea raven in the Bay of Fundy, New Brunswick. In both provinces, T. cottidarum Dogiel, sensu lato, occurs on shorthorn and longhorn sculpins. Two species of fish from brackish pools (the threespine stickleback in both areas; the mummichog in the Bay of Fundy) are often heavily parasitized by T. tenuidens Fauré-Fremiet. All the ciliates referred to were collected from the gills of their hosts, only two of which bore peritrichs other than trichodinids. One of these, Caliperia brevipes Laird, is found on the little skate in the Bay of Fundy and has been described elsewhere. The other, Scyphidia arctica Zhukov, is now reported from the longhorn sculpin in Newfoundland. Only five (16%) of 31 species of marine fish from Newfoundland bore trichodinids, as compared with nine (35%) of 26 from New Brunswick. However, four of the latter group had extremely light or sporadic infestations. Three of the rest, showing high incidence and heavy to extremely heavy infestations, were sculpins (Cottidae), as were three of the five Newfoundland hosts. Thus, while information is accumulating to suggest that marine fish trichodinids find optimum environmental conditions where mean seawater temperatures are not extreme (neither very warm nor very cold), certain fish are evidently more prone to infestation than others. This may well be due to varying ecological vulnerability to parasitization rather than to the operation of host specificity, an important question which, like that of environmental tolerances, merits early experimental attention. The paper includes a list of 61 species of Trichodina and the closely related Tripartiella and Trichodinella now known from marine and euryhaline fish, their validity being assessed on the basis of technique and the taxonomic criteria used.

This paper is a study of base sequence relationships in blackflies by DNA–DNA hybridization. The species used are: Simulium venustum, S. tuberosum, S. vittatum, Cnephia dacotensis, and Prosimulium multidentatum. The midpoints of thermal transition and the buoyant density in CsCl were determined for the DNA of each species and the percent G + C estimated. With the filter method of hybrid formation, maximal yield was obtained at 60 °C; 24 h was found to be a practical length of time for incubation. When the amount of DNA on filter was varied, the homologous reaction reached a plateau at about 50% of the input radioactive DNA; the heterologous reaction reached a plateau at a lesser value in a species-dependent manner. The results indicate a close relationship between S. venustum and S. tuberosum, a more distant one between these species and S. vittatum, and an intermediate one with C. dacotensis. Prosimulium multidentatum shared very little homology with members of the other genera. A precise quantitative evaluation of the results is difficult owing to the complexity of interacting factors. Interpretation would be aided by knowledge of genome sizes and intragenome repetition frequencies. Appropriate studies are underway.

This paper contains a taxonomic survey of nematodes belonging to the predaceous family Mononchidae, collected by Dr. Fields Caveness in western Nigeria during 1959–61. Four genera, new to science, Crassibucca, Hadronchus, Polyonchulus, and Prionchulellus, and 16 new species, Crassibucca penicula, C. macrocauda, C. microdonta, Hadronchus bisexualis, H. monohystera, Iotonchus acuticaudus, I. clarki, I. nigeriensts. I. parabasidontus, I. tarjani, Miconchus pararapax, M. thornei, Mylonchulus curvicaudus, Polyonchulus cobbi, P. megadontus, and Prionchulellus cavenessi are described and illustrated.Several already described species are also included. Iotonchus piracicabae (Lordello) and Mononchus (I.) piracicaboides Carvalho are placed in synonymy of I. trichurus (Cobb). Miconchus dadayi (Micoletzky) in Schneider, 1953 is considered a synonym of Miconchus pararapax n. sp. Miconchus dadayi (Micoletzky, 1914), (=Mononchus macrostoma of Daday, 1910) is regarded as species inquirenda. Mylonchulus hawaiiensis (Cassidy) is removed from synonymy, and Iotonchus similis (Cobb) is designated incertae sedis. Mylonchulus montanus (Thorne) is considered a synonym of Mylonchulus lacustris (Cobb). An illustrated taxonomic key to the 14 genera in the family Mononchidae is presented. Keys to most of the world species in these genera are also included.The value of the tuberculate and non-tuberculate valve as a generic character is discussed.

A method for preparing life tables is described and two examples are presented, based on field data from the Green River Watershed in northwestern New Brunswick. Column headings for age interval (x), survivorship (lx), deaths (dx), and death rate (qx) are adopted from human life tables. An additional column, dx factor, should be added to insect life tables so that the different mortality factors can be tabulated. Life tables for the spruce budworm are based on intensive population sampling on permanent plots, complemented by data on fecundity, natural and applied control factors, and dispersion. Techniques for these basic studies will be detailed in subsequent papers. Life tables for consecutive generations of the budworm in different forest types should provide fundamental information on the epidemiology of the species and on the possible reduction of damage through forest management and through direct control measures.

In this paper I give the first authenticated account of copulation occurring above ground in Richardson's ground squirrels. Copulation occurs in a dorso-ventral position with both animals lying on their sides, and is characterized by a high degree of agonism between the pair.

Survival rates of released rehabilitated birds are rarely known. This paper describes the winter release of two Merlins (Falco columbarius), treated for ulnar fractures, in Saskatoon, Sask. Telemetry was used to maintain contact with one of these birds during the postrelease period, while the progress of the second was monitored through yearly nest surveys. Successful release is defined for Merlins as survival for at least 4 weeks. The first bird survived for 51 days, while the second lived at least 2 years and produced 10 young.

In our original paper (Bergerud, A. T., Mossop, D. H., and Myrberget, S. 1985. Can. J. Zool. 63: 2240–2248) we presented a precise diagram of two major hypotheses on the mechanics of change in ptarmigan numbers: H1, territorial limitations determine breeding numbers, and H2, breeding success determines breeding numbers. We accepted H2 based on a review of the literature and the reanalysis of 11 population studies. Watson and Moss (Watson, A., and Moss, R. 1987. Can. J. Zool. 65: 1043–1047) have not provided a rebuttal to H2 based on data or reanalysis; we believe their arguments are largely semantic. We have pointed out several weaknesses in their choice of study areas and study populations, the most serious being the problems of ingress and egress that confound an understanding of how reproductive and mortality rates change numbers. Further progress requires that they clarify their views; if they still believe in H1, they should state what they will accept as a valid disproof of their territorial model.

This paper documents the occurrence of a small fish species, the threespine stickleback (Gasterosteus aculeatus), in the open North Pacific Ocean. Sticklebacks were incidentally caught in 77 of 4138 (1.86%) purse seine sets for Pacific salmon and were found in the stomachs of 31 of 639 (4.85%) steelhead trout (Salmo gairdneri) caught on the high seas. If destined to reproduce, these pelagic sticklebacks would be an exception to the general rule that long distance migration is undertaken only by large fish species, but it is also possible that they were isolated from breeding populations.

In 1977, more than 11 000 mosquitoes were collected at Boivin Lake, Granby, and examined for ectoparasitic water mites. Mosquitoes of the genera Aedes, Anopheles, Culex, and Mansonia were parasitized by water mites of the families Hydryphantidae and (or) Arrenuridae. There are 11 new host records presented in this paper. Mosquitoes were found parasitized by two different species of mites on six occasions.

This note is a critique of Matsuda's 1982 paper (R. Matsuda. 1982. Can. J. Zool. 60: 733–749) in which he discussed the mechanisms involved in the evolution of the terrestrial Talitridae or landhoppers.

This paper describes a pair of convoluted structures tying on either side of the digestive tract in the mesothorax of Lytta nuttalli Say. They are absent in all the larval stages, but in both sexes of the adults they are equally well developed. They are also found in Lytta viridana LeConte. Each structure has two distal branches ending blindly in the thorax and a short proximal portion leading to an external opening via a prominent reservoir. Histologically they are typically glandular in appearance and show definite indications of secretory activity. They are not thought to secrete either saliva or cantharidin, but rather to produce a pheromone which mediates the formation of protective aggregations of the insects. This type of gland is not known to occur in any other family of insects.

The report by Zach (Zach, R. 1979. Behaviour, 68: 106–117) that Northwestern Crows (Corvus caurinus), when breaking whelks, drop the shells from an optimal height is reexamined. The currency used by Zach is arguably inappropriate because of the significant handling costs incurred by the birds in the shell-breaking process. As the birds ascend to a lower height than is predicted by any of the optimality models examined in this paper, it is suggested that their behaviour should not be cited as an example of the successful application of optimal foraging theory.

Although Duncan (K. W. Duncan. 1985. Can. J. Zool. 63: 2230–2232) holds, "there can be little point in taking Matsuda's thesis seriously," this author argues that some of the ideas found in Matsuda's paper (R. Matsuda. 1982. Can. J. Zool. 60: 733–749) are actually a refinement of Waddington's notion of "genetic assimilation" by means of "canalization." The latter term implies not only the rigidity of the genotype but also its flexibility; it was this quality, plasticity, that Matsuda laboured to examine but that Duncan failed to appreciate.

Evolutionary thinking of sexual strategies has been shaped by a stimulating paper by R. L. Trivers on parental investment and sexual selection. However, there is a major problem in the practical application of the concept of parental investment to those systems in which both males and females offer a substantial amount of parental investment in each offspring, but where the investment of each parent takes different forms. Quantifiable measures (i.e., currency) of the investments of each parent can be of different units (in terms of time, energy, and a risk factor) and hence not additive, and thus one cannot predict who will be the choosier sex.

This paper records seven species of nematodes, none of which are new, and a number of immature forms from Lan Yü, Formosa.

The 26th annual meeting of the Canadian Society of Zoologists, held in May 1987, included a symposium entitled Molecular Studies of Animal Systems. Certainly, a recent and pervasive research thrust in the study of animals has been the accessibility of molecular biology techniques to complement existing research strategies. In organizing this session, Dr. Marilyn Scott had two major objectives: first, to demonstrate how studies at the molecular level facilitate an understanding of the biology of animals and second, to use examples of research programmes that would be of interest to zoologists, in particular those concerned with insect and fish physiology, parasitology, and evolutionary biology. An attempt was made to provide some breadth without being too divergent. The specific research topics derived from the original lectures and included in this issue of the Canadian Journal of Zoology describe and discuss (i) molecular commonality of cuticular and genomic structures between a free-living nematode and a parasitic one, (ii) regulation of vitellogenesis in the locust, and (iii) characterization at the molecular level of fish antifreeze proteins. These papers illustrate how various molecular biology methodologies can be used to resolve problems of biological interest.