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Fleas Leptopsylla segnis, Ceratophyllus consimilis and C. laeviceps were infected with various numbers of Listeria by the method of individual dose feeding through capillary. All three species infected with Listeria, preserve them up to 15 days, excrete them with faeces and transmit them to white mice through biting. The author gives optimal (10³—10⁴ microbial bodies per individual on the average) infecting doses with Listeria for L. segnis that suggests the specificity of relationships between this species and Listeria and a possible role of this species in the transmission of Listeria from rodent to rodent in nature. According to this character, fleas of voles, C. consimilis, can also take part in the circulation of the agent. Interrelations between Listeria and C. laeviceps, fleas of gerbils, are not, apparently, of specific nature.

The authors established the developmental period and survival rate of preimaginal phases of Ctenophthalmus orientalis Wagn. at temperatures from 8 to 30° and relative humidity from 50 to 95%. Minimum developmental periods and the highest survival rate were observed at 20—25° and relative humidity from 80 to 90°. The whole life cycle of fleas from egg to imago under these conditions lasts, on the average, 22 days. Ct. orientalis are more sensitive to changes in humidity than to those in temperature. At the humidity lower than 70% larvae die. The decrease in temperature prolongs the developmental period and affect but little the survival. The threshold of development varies from 5 to 6°.

As a result of examination of various animals (41 species), nests of rodents and dwellings of man in the Pavlodar district 5650 fleas of 48 species and subspecies were collected. Mass species were recognized. The paper deals witn the distribution of fleas throughout the investigated territory and their adaptation to the main types of landscapes.

The spermatheca darkening rate in females of the genus Xenopsylla, as the main character of "adult" fleas, depends to a great extent on the number of feedings and the temperature of the environment. The rate required for spermatheca darkening decreases with increasing temperature and number of feedings. The transition of young individuals to a group of adult fleas occurs in X. nuttalli earlier than in X. skrjabini that suggests more intensive physiological processes in their organism.

The paper contains a description of larvae of five species of gad flies, Hybomitra lapponica Wahlbg., H. tarandinoides Ols., Atylotus miser Szil, Haematopota tamerlani Szil., Tabanus takasagoensis Shir. Characteristic morphological differences between larvae of these species are given.

Accumulation of reserve substances in the yolk glands of platyhelminthes is a subject to a very strict regularity. In those cases when the development of eggs proceeds in the environment glycogen or fat are accumulated in the yolk glands. Entering together with yolk cells into the complex egg they are the only source of energy for a developing embryo. If the development of eggs carries out in the uterus of the worm reserve substances necessary for embryogenesis are provided by the maternal organism. In trematodes, unlike other platyhelminthes, yolk glands can accumulate only glycogen.

The author describes new trematodes from marine and freshwater fishes. Parasaccocoelium mugili Zhukov gen. et sp. n. was found in the intestine of Mugil so-iuy Bas., Hapalotrema flecterotestis Zhukov gen. et sp. n. — in the intestine of Liocassis brashnicowi Berg and M. so-iuy, Haplosplanchnus bivitellosus Zhukov sp. n. — in the intestine of Mugil cephalus (L.) and M. so-iuy, Isocoelioides orientalis Zhukov gen. et sp. n. — in the stomach, pyloric appendages and intestine of Lateolabrax japonicus (Guv. et Val.), Paraphilopinna fluvialis Zhukov gen. et sp. n. — in the ureter (once in gonade) of Misgurnus anguillicaudatus (Cantor) and liver (larva) of Lateolabrax japonicus. The material was collected in the Possjet Bay (the basin of the Japan Sea) and the Liao Ho river (the basin of the Yellow Sea).

Sizes of body, chitinoid armature of the haptor (their shape too) and copulatory complex of mature Dactylogyrus auriculatus and 12 other species of the genus, Tetraonchus monenteron and Diplozoon megan from young fishes and those of older ages are not identical. Most of dactylogyrus from young fishes have the above mentioned structures less by 20—50 per cent than those of the generations from mature fishes. The greater differences are between specimens from fishes 0+ — 3+ or 0+ — 1+ (the period of the most intensiv growth of fishes). The greatest difference is in D. auriculatus (between specimens from 0+ to 13+).

The paper contains a description of clamps in Tagia gempylli Dillon et Hargis, 1965 from original material. The analysis was undertaken of the structure of these clamps in comparison with those of T. ecuadori (Meserve, 1938) and various representatives of the families Discocotylidae, Anthocotylidae and Diclidophoridae. Results of the analysis have shown that the genus Tagia Sproston, 1946 should be referred to the family Diclidophoridae and the subfamily Tagiinae Yamaguti, 1963 is invalid.

The authors give a more precise definition to the notion of "helminths" as representatives of the supertype Scolecida leading a parasitic mode of life. In the authors'opinion the term "parasitic worms" accepted by Russian scientists is not a synonym to the term "helminths".

The spread of whirling disease in trout farms of the USA and researches on this disease are characterized. The control measures for the spread of whirling disease are given. The author reports on the federal laws against further spread of the disease.

Microsporidiosis of crawfishes is insufficiently studied. Our investigations have shown that the infection proceeds both by alimentary way and transovarially. Microsporidians parasitize skeletal and cardiac musculature as well as ovary and developing eggs of crawfishes. The type of development of Thelohania contejeani is very similar to those of other members of this genus. The whitening of muscles so characteristic of this disease sets in only after full maturation of spores.

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