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Laelaps neacomydis n. sp. is described from the pelage of the rodent Neacomys spinosus collected in Bolivia. Collection records from northern Brazil, southeastern Peru, and central Bolivia indicate its wide distribution across Amazonas associated with rodents of the genus Neacomys. The formal taxonomic description and illustrations are derived from the adults (female and male). Two larger species of laelapine mites, Gigantolaelaps intermedius and L. boultoni, infest the same hosts at the same localities.

The present study was carried out in 3 villages, namely Kafr Ayoub Soliman, Kafr Ibrahim El-Aidi, and El-Sa'adat, Sharqiya Governorate, Egypt. A total of 519 rats was collected from the 3 study sites: 46.6% Rattus rattus, and 53.4% Rattus norvegicus. A total of 20,643 ectoparasites was recovered from R. rattus: 33.3% mites, 33.8% fleas, and 32.9% lice. From R. norvegicus a total of 40,997 ectoparasites was recovered: 28.9% mites, 31% fleas, and 40.1% lice. Three common mite species were recovered from both rat hosts, i.e., Ornithonyssus bacoti, Radfordia ensifera, and Laelaps nuttalli. Three common flea species were also recovered from both rat hosts, i.e., Echidnophaga gallinacea, Leptopsylla segnis, and Xenopsylla cheopis. Polyplax spinulosa was the only dominant louse species that infested both rat hosts. Rats did not show a definite breeding season, and the seasonal rat indices were generally low in different study sites. There were no significant differences between the prevalence of each of mites, fleas, and lice in both rat species. The total general indices of mites and fleas, on the other hand, was significantly higher in R. norvegicus. The general index of X. cheopis was high and ranged between 5.9 in R. rattus and 14.5 in R. norvegicus. Season-related changes were observed in the general index of each of L. segnis infesting both rat species and R. ensifera and O. bacoti infesting R. norvegicus. The prevalence and general indices of some ectoparasites showed differences related to the locality of their rat hosts. Seasonal changes in the general indices of some ectoparasites paralleled seasonal changes in the relative abundance of their rat hosts.

Examination of 165 rodents trapped in domestic, peridomestic, and feral biotopes of central and southern India revealed the presence of 1,359 mesostigmatid mites. Rodents in central India were infested with 1 species of mite, Laelaps nuttalli; 98% of these mites were recovered from the peridomestic rodent Bandicota bengalensis. Material from the burrow nest of a peridomestic rodent examined in central India revealed the mite, Hypoaspis miles. Rodents from the diverse biotopes of southern India were infested by 8 species of mites: L. nuttalli, Laelaps buxtoni, Laelaps myonyssognathus, Androlaelaps aduncus, Androlaelaps marshalli, Androlaelaps sp. A, Hypoaspis sp. 1, and Hypoaspis sp. 2. Sheep from nearby villages regularly graze in feral biotopes. From the hair of these sheep, 2 species of mesostigmatid mites were recovered, A. aduncus and A. marshalli. The sheep appeared to aid the dispersal of rodent-infesting mites passively. Laelaps nuttalli was the predominant mite species found on the peridomestic rodent B. bengalensis. In both central and southern India, the prevalence, mean intensity, and relative density of this mite were much higher on peridomestic rodents than on domestic and feral rodents. A significant negative correlation was found between the numbers of mites and fleas infesting rodents in central India. A highly significant positive association between A. marshalli and A. aduncus on the feral rodent Tatera indica was recorded. In southern India, the overall prevalence of the 8 species of mites was highest on Mus platythrix. However, the combined prevalence of these mites on 2 feral rodents T. indica and M. platythrix was lower than their prevalence on B. bengalensis. Similarly, the combined values for mean intensity and relative density of these mites on the 2 feral rodents were lower than on the peridomestic rodent B. bengalensis.

Among the collections made by the author in 1953 as part of a study of the parasitic mites of Mexico were many robust, active acarines from pocket mice, Liomys spp. These have been identified as Laelaps liomydis Grant. Through the courtesy of Lieutenant Colonel Robert Traub a collection of parasitic mites from Venezuela was made available for study and comparison with the Mexican fauna. Among these were numerous specimens from Heteromys and other rodents which represent a new species of mite closely related to L. liomydis. Study of these forms was facilitated by the loan of the allotype male and a female specimen of L. liomydis by C. Donald Grant, and the loan of a cotype of Liponysella madagascariensis (Hirst) by the British Museum of Natural History. Identifications of Mexican mammals were made by Drs. Bernardo Villa R. and Seth Benson. Dr. E. W. Jameson, Jr. kindly offered helpful comments on the manuscript. It is the author's belief that L. liomydis and the new species described here represent a new genus. Grant (in litt.) agrees with this interpretation.

In agar-gel tests, extracts of Psoroptes cuniculi (Delafond), against the sera of rabbits with ear canker, a disease caused by this mite, resulted in precipitation bands indicating at least two antigenantibody systems. Agar-gel double diffusion techniques can be used to show antigen-antibody systems resulting from natural infection of man and animals with helminth parasites (Kagan and Norman, 1963). But antibodies naturally produced against different species of arthropods when they invade the tissues, suck blood, inject venom, or act as allergens have not heretofore been demonstrated by such methods (Langlois et al., 1963). Blacklock et al. (1930) first demonstrated precipitins in guinea pigs to insect parasites. Little progress seems to have been made since that time. This paper reports results with agar-gel tests which confirm those of Culbertson (1935) obtained by the ring test. MATERIALS AND METHODS The serum samples came from rabbits involved in an outbreak of ear canker, scab, or psoroptic mange in the animal houses of two separate institutions. It was acquired and spread naturally, without deliberate human intervention. In all, sera from 25 rabbits exposed to the epidemic, including clean rabbits as well as scabby ones were studied. Of these, two rabbits were severely affected as follows. The first case, G-7, was a small extremely thin animal weighing 3 to 4 lb. Thick, dry grayishbrown crusts completely filled both ear canals and extended over both surfaces of the ears without interruption (Fig. 1). The remainder of the body was covered with the same type of exudate. The thickness of the crust varied from approximately 0.75 to 1.0 cm over the head, back, and feet to about 2 mm over the abdomen. Many mites were seen on the bare surface of the skin after removal of the scabs and hair. The other severe case, rabbit No. 4 had extensive crusts in both ears with large quantities of grayish yellowish odorous pus. Received for publication 8 August 1966. * This investigation was supported in part by Research Grant AI-03821 and Graduate Research Training Grant 5-T1 AI 15 from the NIAID, U. S. Public Health Service. Two large abscesses below the right ear were opened and drained. Swabs were made and scabs collected for bacterial and fungal cultures. Mites were recovered from the scabs and identified. Scabs from rabbit G-7 were put in 250-ml beakers each containing about 100 ml of merthiolated physiological saline. Three such beakers were filled and stored in the freezer. Later pieces of the material were thawed and searched for mites using a stereoscopic microscope. Literally thousands of specimens of the scab mite Psoroptes cuniculi (Delafond) were found. There were also some specimens of Notoedres cati (Hering) (-Sarcoptes cuniculi Gerlach, according to Lavoipierre, 1964) and Listrophorus gibbus Pagenstecher, but they were not sufficiently abundant to be used in this study. Extracts of Psoroptes cuniculi were prepared directly without lyophilization. Large mature specimens were removed with forceps, weighed, and homogenized in saline solution with merthiolate at 1:5,000 in a tissue grinder to give dilutions at 1:5 and 1:10. About 1,200 specimens weighed 30 mg which when diluted in 0.3 ml (300 , liters) of saline provided sufficient extract at 1:10 to make six agar-gel slides. More than 40,000 specimens were obtained from rabbit G-7, enough material to provide extracts for most of the tests. The bacteria Pseudomonas aeruginosa, Proteus species, Diphtheroid species, and Staphylococcus aureus were cultured on blood agar, and Aspergillus species was cultured on Sabouraud dextrose agar from the material obtained from rabbit No. 4. Extracts were made of each of these by scraping the agar, weighing, homogenizing in a hand tissue grinder, and diluting 1:10 in merthiolate saline without the intention of disrupting or disintegrating the bacteria and mold. Extracts of adult females of the yellow fever mosquito, Aedes aegypti and the southern house mosquito Culex quinquefasciatus were made from material obtained from laboratory colonies (Fox et al., 1963). A laboratory colony also provided the material for extracts of the domestic rat mite, Laelaps nuttalli Hirst. For agar-gel tests, the microslide technique of Yakulis and Heller (1959) was used with SeaKem( Agarose.

The new genus and species Protonyssus uniscutatus was described by Turk (1946) from a single female specimen taken from the skin of a rodent, Proechimys calidius calidius Thos. captured in Northern Ecuador. Since Protonyssus Turk is a homonym of Protonyssus Trouessart, 1915, Baker and Wharton (1952) replaced it with the name Tur. Recently the authors received collections of parasitic mites through the courtesy of Mr. Eustorgio Mendez and Captain Robert M. Altman. Among them were many mites from Panamanian Proechimys which bore a close resemblance to the description and figure given by Turk for Tur uniscutatus. Since Turk's description was based on a single specimen, mounted in balsam, it seemed possible that the differences noted from our specimens might be more apparent than real. With the cooperation of Dr. Turk the type of Protonyssus uniscutatus was located at the Hope Department of Entomology, University Museum, Oxford, and made available for study through the kindness of M. W. R. de V. Graham. It was found to be identical with the Panamanian material, but due to its dorsal orientation and the type of mounting medium used, certain critical misinterpretations of structure were incorporated in the original description and figure by Turk (1946) causing him to place the genus in the family Macronyssidae. The description states that the digits of the chelicerae are devoid of all traces of teeth, whereas actually the fixed digit has a definite, although small, subterminal tooth. The "presternal" area of the sternal shield does not actually overlap the sternal plate as originally described, although superficially of that appearance in the type. The "very strong, slightly incurved line delimiting the genital shield from the ventral one" described by Turk is actually an internal sclerotization; the genital portion of the shield is not demarcated from the ventral portion. The anterior extremity of the genital area is slightly flared and fan-shaped, but is distinctly separated from the metasternal platelets. The genus Tur is considered here as a typical member of the family Laelaptidae with close relationship to the genus Laelaps.

Laelaps nigeriensis sp. n. from Nigeria is described. Type material was taken from Crocidura sp. and from Mus (Leggada) musculoides at Adu, Nigeria. The species is distinctive in lacking spurlike setae on coxae I, and in that the inner members of the paired hypostomal setae extend posteriorly to level of insertion of gnathosomal setae. The species description given in this paper is based upon specimens collected by the late Dr. A. S. Pearse in Nigeria in 1926. These specimens, and others taken from rodents and insectivores by Dr. Pearse, were forwarded to the United States National Museum and later referred to the writer for study. Subfamily Laelaptinae Berlese, 1892 Laelaps Koch, 1839 Laelaps nigeriensis sp. n. (figs. 1, 2) Female: Terminal setae of dorsal shield over twice as long as subterminal setae. Presternal area not clearly distinct from sternal shield. Anterior sternal shield shortest; anterior pores parallel with anterior margin of shield, but posterior pores set at an angle; length-width ratio of shield about 3:4. Endopodal setae at least as long as posterior sternal setae. Genitoventral shield slightly expanded posterior to coxae IV; its posterior margin very slightly rounded between posterior genitoventral setae; anterior genitoventral setae largest and slightly farther apart than anterior sternal setae; posterior genitoventral setae slightly farther apart than those of anterior pair. Anterior margin of anal shield slightly concave; anus slightly closer to anterior margin of shield than to postanal seta; paired anal setae at level of posterior end of anus; length-width ratio of shield 1:1; cribrum very narrow. Metapodal shields irregular ovals. Nine or ten pairs of ventral setae; peritreme extends to level of coxa I. Chelae not distinct; it cannot be determined whether the pilus is inflated; inner paired hypostomal setae at least four times as long as outer setae and extending posteriorly to level of point of insertion of gnathosomal setae. Lengthwidth ratio of tarsus I 2.5:1; femora I and II with elongate dorsal setae, which are smaller than most setae on dorsal shield; coxae I and IV without spurlike setae; coxae II and III each with one Received for publication 26 September 1961. * Lt. Colonel Keegan is assigned to the Entomology Branch, Department of Preventive Medicine, Medical Field Service School, Brooke Army Medical Center, Fort Sam Houston, Texas. spurlike seta. Idiosoma of holotype female 538 ,u in length and 370 tu in width; idiosoma of a paratype female, on same slide with holotype, 577 ,L long and 337 A wide. This specimen is less flattened than the holotype and is probably more representative of the normal size of the species. Male: Unknown. Type material: Holotype and paratype female, on same slide, taken from Crocidura sp. at Adu, Nigeria, 15 September 1926, by A. S. Pearse. One additional paratype, taken from Mus (Leggada) musculoides at Adu, Nigeria, by A. S. Pearse on 28 September 1926. Type material in United States National Museum. Discussion: Absence of spurlike setae on coxae I places Laelaps nigeriensis in a category with L. simillimus Zumpt, 1950; L. transvaalensis Zumpt, 1950; L. grenieri Taufflieb, 1954; L. keegani Thurman, 1958; and L. congoicola Taufflieb, 1959. Only in nigeriensis does the inner member of the paired hypostomal setae extend posteriorly to the level of insertion of the gnathostomal setae. The drawings were prepared by Mr. Saburo Shibata, Taxonomic Section, Department of Entomology, 406th Medical General Laboratory. Slide preparations of types were made by Miss Yoshiko Yoshida of the same laboratory.

Murine typhus fever in Puerto Rico is seasonal favoring the months of May, June, July and August when the number of cases reported almost always exceeds that of the remainder of the year. The disease is also urban and the majority of the cases are said to occur in the city of San Juan. An ectoparasite survey of the rats of San Juan, therefore, should show a prevalence of the vectors which is in accord with the seasonal variation of the disease and such arthropods ought to be among the most common ectoparasites of the city's rats. Of the many species of arthropods parasitic upon or associated with the rats of San Juan, six are so abundant as to merit special consideration. They are Xenopsylla cheopis (Rothschild), Echidnophaga gallinacea (Westwood), Polyplax spinulosa (Burmeister), Bdellonyssus bacoti (Hirst), Laelaps nuttalli Hirst and Ornithodoros puertoricensis Fox, of which the first four have for some years been known to be experimental transmitters of rodent typhus. What has been found out about the relative and seasonal abundance of these species in San Juan is given in the following pages. The municipality of San Juan is located on a peninsula with San Juan Bay to the south and the Atlantic Ocean to the north. On the point of the peninsula is the old city or San Juan proper which except for a coastal suburb known as La Perla and an ancient military post, El Morro, contains commercial buildings and apartmenthouse type residences. The streets are paved with no empty lots, lawns or vegetation to speak of, and there is considerable activity out-of-doors day and night among the people. A short distance inland lies the district called Puerta de Tierra made up of various types of buildings, including residences, commercial establishments, warehouses and wharfs, with empty lots and some unpaved streets. On the base of the peninsula is Santurce, separated from Puerta de Tierra by a well-bridged estuary, it is mainly residential, the houses being for the most part small with front and back yards; empty lots, unpaved streets and vegetation are common, and in the district are varying socio-economic conditions which influence greatly the types of construction present. As regards the places from which the rats came there was little ecological difference between the Santurce and Puetra de Tierra localities. The traps used were of the wooden box type baited with fresh bread. They were set in the backyards or under the houses (sometimes in them) of the poorer sections. The houses were usually small, frame structures, far from rat-proof and rats were reported to run in and out of them from the unpaved ground around them. The residents being not well-off economically were not very successful as a rule in maintaining the environs of their homes on a plane in accord with modern sanitary standards. In San Juan proper very different ecological factors obtained. Here unbaited steel snap traps