often fused to form a coxal plate. The tarsi usually end in two claws, while numerous long hairs arranged either singly or in tufts along the legs aid the mites in swimming. This process is usually eratic and slow. Nearer the posterior end of the venter is the genital area, margined on either side by flaps or reniform areas provided with sucker-like disks, the number and arrangement of which are useful specific characters. One or two pairs of simple eyes are usually present. The body integument may be soft and leathery or hard and is often finely pitted or otherwise ornamented. The mouthparts are frequently hidden from view by the projecting edge of the cephalothorax. The pyriform beak is seldom conspicuous. The mandibles are two jointed and may terminate in a claw-like joint or be elongated into stylets. The four or five jointed palpi frequently have the distal joint long and folded back against the penultimate. These organs vary greatly in shape and are much used in classification. Most species are free-living and predaceous; but several genera, Unionicola in the gills of mollusks and Hydrachna and several other genera on aquatic insects, are parasitic. The latter frequently attach to adult insects and when these leave the water the mite parasites soon die from exposure to the air. The eggs of these mites are usually spherical. They are deposited on various submerged supports. As the embryo develops the egg membranes separate and a deutovius stage results. The six-legged larvae are usually some shade of red or green and only slightly resemble the adults. The short hooked palpi enable them to retain a hold upon plants, etc. As engorgement procedes the legs are seemingly absorbed and the mites appear as egg-shaped sacks. These are often found attached to aquatic insects. Within these a quiescent stage is formed from which the adults will appear. I have records of eight species and one variety in six genera taken in Ohio. Seven species and one variety were taken in Buckeye Lake, Ohio during late August, 1923. Dr. Marshall has made determinations of these collections. The genus Arrhenurus has a short, entire, shield-shaped capitulum; the fifth joint of the short, stout palpi forms a claw to an apical extension of the fourth; the eyes are widely separated and not in a capsule; and the thick integument is pierced by large pores. These mites are usually bluish-green in color. Arrhenurus trifoliatus Marshall Trans. Amer. Micr. Soc., XXVIII, 1908, p. 115 This is a dull olive green species measuring about 1.02 mm long by .75 mm broad. I have taken several specimens among the plankton in the west and southwest lagoons of Buckeye Lake. The species is recorded from several of the north central states and is probably well distributed in this region and southern Canada. Arrhenurus marshalli Piersig A number of specimens ranging in color from pale brown to olive green were taken in various parts of the western lagoons of Buckeye Lake, Ohio. All the material came from the bottom of shallow lagoons covered with quantities of decaying vegetable material. It is also reported from Bass Island in Lake Erie and from numerous places in the United States and southern Canada. The species in the genus Unionicola were long grouped under Atax, but the latter name is now invalid in this sense. These mites have but few swimming hairs on the legs; the genital opening is at the tip of the body and the plates at either side of it bear more than three easily distinguished disks. The epimera are usually not united into one plate and the fifth palpal joint does not form an opposable claw to the preceding. Species are recorded from all parts of the world and are always parasitic in the gills of fresh water mollusks during some part of their life. Unionicola crassipes Muller Zool. Dan.. Prodr. 1776, 2254, p. 189 This species is peculiar because of the great length of its legs. Specimens in my collection range from pale brown to olive green and almost black when alive. Mature females are about 1 mm in length, the males but half this size. It is one of the most common species in Buckeye Lake during late August. A large number of mature males, females, and deutonymphs were taken in the upper three feet of water. The species is also recorded from Europe, Palestine, several of the north central United States, and southern Canada. The genus Neumania are mostly soft bodied mites. The epimera are large and grouped; the palpi are small, terminating in three or four finger-like processes; the fore legs are stout and bear numerous dagger-like spines set in papillae on the mid-joint. Neumania distincta Marshall Trans. Wis. Acad. Sci. Arts. Lets., XX, 1922, p. 210 This is a large species, the male measuring a little more than 1 mm in length. I have taken no females, and Dr. Marshall states that none are on record. The genital plates are characteristic being narrow near the middle and extending far out from the genital opening. But one specimen, olive green in color, was taken in the southwest lagoon of Buckeye Lake. It is also recorded from Wisconsin but appears to be a rare species. Neumania punctata Marshall Trans. Wis. Acad. Sci. Arts. Lets., XX, 1922, p. 211 The geni I have but The females of this species are about .75 mm long. tal plates are large and lie close to the fourth epimera. one specimen, a pale brown male, from shallow water in the southwest lagoon of Buckeye Lake. Dr. Marshall records the species from Wisconsin. The genus Limnesia contains but few species, however, from all parts of the world. They are peculiar in having no claw on the posterior pair of legs, which terminate in a long slender spine. The body is usually soft and highly arched. The two eyes on either side are not fused as is often the case in mature hydrachnids. Limnesia paucispina Wolcott Trans. Amer. Micr. Soc. XXXV, 1903, p. 98 Dr. Wolcott distinguishes the species by the stouter palpi with a short papilla on the second segment; the scarcity of spines on the appendages; and the character of the genital area. The females are about 1 mm long and .8 mm broad. This is a common species in Buckeye Lake during late August. Many males and females were taken swimming in or near plankton. It is probably a fairly common species in the north central states. Limnesia histrionica var. wolcotti Piersig These are pale green, solf-bodied mites measuring about 2 mm long by 1.7 mm broad. The species L. histrionica Hermann is widely distributed thruout Europe and North America. Two specimens of the variety, both immature females, were taken near the bottom of a shallow pool in the southwest lagoon. In Tyrrellia there are no swimming hairs on the legs; the fourth pair end in claws; the second palpal joint bears no spines; the epimera are in four groups with the genital area lying between the fourth pair; the distal palpal segment is not opposable to the preceding. Tyrrellia circularis Koenike Abh. Ver. Bremen, XIII, 1895, p. 199 This is a greenish species about 1.3 mm long by 1 mm broad. It is recorded from North America and to my knowledge is the only species in the genus. The type material is from Illinois. Brain took the species from a board in the Black Channel near Cedar Point, Ohio, August 15, 1912. It is not a common species. Piona, long known as Curvipès, contains many species in all parts of the world. The body is soft and all the legs have swimming hairs. The hind epimera are smooth; the palpi smaller than leg I and terminating in 2 or 3 small claws; the fourth segment has two papillae below; and the genital opening is not at the tip of the body. Piona rheigardi Wolcott Trans. Amer. Micr. Soc., XXIII, 1902, p. 235 This small, blue-green species is about .8 mm long by .6 mm broad. The palpal form and the genital area distinguish it from other species. It is quite common in all shallow waters of Buckeye Lake, and is recorded from other places in North America. In addition to these records I have undetermined material in Hydrachna, Diplodontus, Sperchon, Hydryphantes, and Torrenticola. Suborder PERITREMATA Those mites in which the tracheae open on each side of the body thru a peritreme or stigmal plate, usually located above the posterior coxae, constitute this suborder. The integument is usually leathery or provided with chitinous plates. It is comprised of two superfamilies including some of our most injurious species. Superfamily Ixodoidea Members of this superfamily are commonly called ticks and are the most common of mites. The tracheal opening is in a discoidal plate; the integument is leathery; and the hypostome is a large dart-like structure projecting from the anterior end of the body and armed with recurved hooks. Because of the parasitic habit of this group of mites they have been intensively studied and the biology of many species is well known. The species are all quite large and even in the larval stage they can be detected with the unaided eye. To even review the general characters would require a large volume and so will not be undertaken here. Unengorged ticks are roundly triangular in shape but when greatly engorged with food or eggs the female assumes the shape of a castor bean and seems to lack legs and a capitulum. They range from 2 mm in small unengorged species to 20 mm in large distended ones. The capitulum bears a somewhat complex structure, the proboscis. The mandibles, the sheath enfolding them, and the hypostome bearing the recurved hooks form this structure. The arrangement of the hooks is of value in specific identification. In feeding, the hypostomes and mandibles are inserted in the host, the hooks of the former making detachment by force nearly impossible without removing a bit of host tissue or injuring the tick. The four jointed palpi are inserted at the sides of the proboscis. The basal and terminal joints are small and quite obscure. On the abdomen, just posterior to the capitulum, most species bear a roughly hexagonal corneous plate or scutum. In the males this covers most of the dorsum but in the females it is quite small. Several porose areas, also on the dorsum, are aids in identification. Their function is uncertain altho all mature females of the family Ixodidae have them. Some genera show eye-like spots on the lateral margin. The posterior abdominal margin of many species has a folded or lobed appearance due to a number of short furrows. These are most apparent in males and unengorged females. When the latter are engorged the furrows are scarcely discernable. The anterior ventral opening is the genital, the posterior being the anal. The males of many species show various chitinized plates about the anus. The legs, usually six jointed, are slender and arise near the anterior end. Each terminates in two large claws at the tip of a pedicel. A median pulvillus is usually present. Haller's organ, a membrane-covered pit on tarsus I, is thought to be auditory in function. A wide range of color patterns is to be found in these Acarina and this character is seldom of taxonomic value. All ticks are parasitic during a part of their life. A large number of mammals, birds, reptiles, batrachians, and a few insects serve as hosts. Usually but little injury results to the host except the loss of blood and this is not serious except where the parasites are very numerous. Those forms which transmit fatal diseases take a toll placed by some as high as $150,000,000 annually. |