Banks records the species as abundant about Fort Collins, Colorado, which would suggest a rather wide distribution in this country.

The genus Erythraeus is similar to the preceding genus but differs in having two pairs of eyes and the posterior pair of legs very long. The old genus Rhyncholophus, for some time, included the members of this genus.

Erythraeus parvisetosus Ewing

Trans. Acad. Sci. St. L., XVIII, 5, 1909, p. 57

This is an almost black species, adults of which measure 2 mm in length by 1.5 mm in width. On September 9, 1923, while collecting insects from cow dung near Chillicothe, I captured several specimens of this species in tunnels made in nearly dry cakes of this material. The abdomens were quite distended. One individual was standing over a mass of small shiny black eggs which she may have been depositing when disturbed. The material was collected in situ and placed in a battery jar. All individuals were later observed laying eggs similar to those already referred to. No adults lived beyond the middle of October. The eggs were placed in conditions that might prevail in the field and the following May nearly all hatched. All died altho I offered them aphids of several species and a number of beetles.

Dr. Ewing records the type material from Muncie, Illinois and states that the adults seem to carry the young upon their backs as parasites. If those adults I have observed did not suffer premature death such a relationship would scarcely be possible. two records mentioned seem to pertain to this species.

Erythraeus phalangiolus Ewing

Bul. Amer. Mus. Nat. Hist. XXXVII, 1917, p. 153

But the

The species is peculiar because of its very long legs, whence its name. It was at first mistaken for an immature phalangid. Adults are 1.7 mm long by 1.4 mm broad. I presume it to be red since no color is given in the original description. The type material collected under elm bark at Xenia, Ohio is the only material known to me.

Erythraeus pilosus Banks

Trans. Amer. Ent. Soc., XXI, 1894, p. 217

This is a bright red species. It is common in southern Ohio from early June to late September, and is probably well distributed over the State. Slight depressions on the dorsum and the covering

of fine hairs reflect light as silvery streaks which seem to ripple across the body as the mite walks. Mature specimens are about 1.5 mm long, and quite active. I have observed no feeding.

Mr. T. D. Jarvis, in the 40th Ann. Rpt. Ent. Soc. of Ontario, 1909, pp. 82-109, records this species as predacious upon the eggs of an Ichneumon sp., on Cecropia moths, and on apple canker worms. I have records which indicate the occurrence of this mite thruout the north central states and southern Canada.

The genus Fessonia is peculiar in having highly retractile chelicerae which are often not visible when withdrawn into the body. These mites also possess five-jointed legs and two pairs of eyes. A third pair of eyes may sometimes be present on the anterior margin of the cephalothorax. But one species occurs in Ohio.

Fessonia longilinealis Ewing

Trans. Acad. Sci. St. L., XVIII, 5, 1909, pp. 61-62

The species was first described as Smaris longilinealis but is now placed in the present genus. It is bright red in color with the legs and mouthparts paler. Mature specimens are very active. They measure about 1.7 mm long by 1 mm broad. I have taken this species from early May until late September thruout southern Ohio. Nymphs are quite abundant early in the season. They occur on the ground in open woods and fields. No feeding has been observed. It is recorded from several of the north central and eastern states and is probably well distributed over this area.

From this presentation of the family Erythraeidae in Ohio one will notice how little is known about the specific habits of a group of mites that are parasitic as larvae and, at least in some cases, predaceous as adults.

Family Trombidiidae

The family Trombidiidae is separated from the preceding in having each of the chelicerae armed with a falcate or jaw-like appendage at its tip and in having a small cephalothorax on a different plane than the abdomen. The separation of the body is prominent and each bears two pairs of legs. All the species known are some shade of red. The body hairs are feathered. The palpi are five jointed and terminate in the claw and thumb. The seven jointed legs end in two claws. There are two eyes on each side of the cephalothorax which are usually stalked. The crista is usually quite prominent. In some species bristles arise from enlarged

areas in the crista. Some authors consider them as pseudostigmatic organs but they are scarcely homologous with the similar structures in the Oribatidae.

This group, popularly known as the "harvest mites," is known to most field observers. In the spring the bright red adults of some species appear in open fields and woods in large numbers. They crawl about in search of eggs or small arthropods upon which to feed.

The eggs are usually deposited in the spring in clusters in small cavities in the soil. The larvae upon hatching are orange red in color, have but six legs, and are quite minute. Those of some species are parasitic upon various insects while others attack the vertebrates. Many have a habit of temporarily fastening themselves to man where they are quite irritating. In oriental countries, several species with this habit transmit fatal diseases.

When engorged the larva drops from its host and usually finds shelter beneath debris or in loose soil. Here it passes into a quiescent stage after which it appears as a nymph possessing four pairs of legs and resembling the adult in all but sexual maturity. Following a brief period of feeding the nymph again transforms into a pupal phase from which the adult appears. The adults may not appear above ground until the following spring, passing the winter in their earthen cell. Parasitism is not recorded for any of the adult or nymphal stages. They are always observed in the role of predators upon some smaller arthropod or its eggs.

Here again the student will be confronted by a confusing synonomy. The genus Trombidium at one time contained all our species but this has been split into many new genera. Many species have been established on larval forms and little attempt has been made to link larva with adult. Representatives of the family are known from all parts of the world. Eight species in six genera are known from Ohio.

The genus Allothrombium has the crista expanded at the middle where it bears a pair of pseudostigmata. There is a conspicuous pulvillus between the tarsal claws. The eyes are truncate. The palpi bear but a single claw at their tip.

Allothrombium pulvinus Ewing

Bul. Amer. Mus. Nat. Hist., XXXVII, 1917, p. 157

This is a large dull scarlet species measuring about 4 mm long by 2.3 mm broad. This separates it from our other species. Mr. C. W. Howard has succeeded in working out the life history of the species.

The eggs are spherical and about .2 mm in diameter. They are deposited during May and June beneath leaves or in loose soil. They are usually deposited in clusters of 100 or 200, with a few silken threads spun about the mass. They hatch in from three to five days, until mid-July. The small, hexapod, scarlet larvae crawl about in search of a host. They often ascend plants or other objects in their path. Several species of aphids serve as satisfactory hosts. One can see how the negative geotropism displayed by the larvae will bring them most readily to an aphis colony. Several mites may attach to one host. They are not known to attack man. Upon engorgement the larva loosens its hold, drops to the ground and makes its way into loose soil for a short distance where it transforms to a nymphal stage. This process takes place during June or July and requires about one week. Nymphs, which greatly resemble the adults in all but size and sexual maturity, feed upon a variety of small insects occurring in their habitat. By early August they again begin to enter the soil, undergo another transformation, and in about two weeks appear as adults. The mature mites are active until frost when they again enter the soil not to appear until the following spring.

I have taken the species in large numbers in hemlock forests about Bainbridge, Ohio during late April and thruout May. Attempts at rearing were unsuccessful. It is recorded from nearly all the north central states.

Allothrombium missouriense Ewing

Trans. Acad. Sci. St. L., XVIII, 5, 1909, p. 63

This species is separated from the preceding in being but 1 mm long and .7 mm wide. It is bright red in color and is one of the most common Trombidians in southern Ohio. Captures of adults date from early June to late September. They have been taken in weeds and trees and other plants where aphids were often abundant. I have observed them feeding but once and then upon a small Heteropteron. No rearing work has been attempted, and to my knowledge detailed life history data are wanting. From observations made, these do not vary greatly from the preceding species.

The type material was collected and described at Columbia, Missouri and this description is the only other printed reference to my knowledge. It is probably well distributed thruout the north central states.

The genus Eutrombidium has a posterior dorsal plate on the abdomen; the pseudostigmatic organs are in the middle of the crista which extends to the base of the cephalothorax; the palpi are armed with two claws; and the body is constricted at the insertion of the posterior pairs of legs. But one species is known from Ohio. Eutrombidium trigonum Hermann Mem. Apt., 1804, p. 26

This mite has been described under various specific and generic names, probably the most common of which is Trombidium locustarum Riley. It is commonly known as the "locust mite" from its usual association with various grasshoppers.

Extended observations on this species have been made because of its larval parasitism on grasshoppers and the habit of the adult of feeding upon Acridid eggs.

The bright red adults, about 3 mm long by 2 mm broad, are common in plowed fields or waste lands during spring. Due to numerous setae on the body the light is reflected as silvery streaks as the mite moves about. Adults were taken from March to late August. A few of those that lived longest were kept in rearing cages containing nothing but damp soil. During years of heavy grasshopper infestation the species becomes very abundant. It has long been known that the adults feed mainly upon grasshopper eggs. They crawl about on the surface and thru the soil crevices searching for eggs. When an egg pod is found they pierce the shell with their sharp chelicerae and withdraw the contents after which the empty shell collapses. Three or four eggs usually suffice to engorge an adult mite. I have records of this species feeding upon the eggs of Melanoplus bivittatus, M. femur-rubrum, M. differentialis, M. atlanis, M. minor, and Stenobothris curtipennis.

The spherical orange-colored eggs are deposited in clusters of several hundred in small cavities in the soil. The minute, sixlegged, orange-colored larvae do not appear until nearly a month following oviposition. About two weeks previous to hatching, the outer egg shell splits and the legs of the embryo project as a nearly hyaline cone still contained within the inner shell. This is called the deutovium stage. Upon hatching the larva crawls about until finding a grasshopper, either nymph or adult. It attaches itself beneath the wing pads or wings, to the wing veins, at the intersegmental commissures, or most any thinly chitinized region of the body. I have found large numbers attached about the mouthparts but have never had them successfully engorge here. They also