258 NEW YORK STATE MUSEUM 



would thus appear, that the Hypopus is a form assumed by the mite 

 when scarcity of food and moisture threaten its extinction. From 

 the Hypopus having been seen by some within the ordinary mite, this 

 has led them to claim that it is but a parasite of Tyroglyphus. 



During my study of this mite, I was so fortunate as to detect in the above- 

 mentioned instance the Hypopus within the body of the female. Numbers 

 have also been seen walking around and finally becoming fixed in their 

 characteristic attitude. The Hypopus appears so evidently to be but 

 another form of the mite, that the idea of its parasitic nature is hardly 



tenable. 



Description of the Mite. 



Examples of the mite were submitted to Prof. Herbert Osborn, who 

 pronounced it a species of Tyroglyphus apparently w^tdcr phylloxerce Riley, 

 but with which he could not make it agree in all details. He further added 

 that it might be identical with some of the described European forms. 

 Failing to find a description of a similar species in the limited European 

 literature at my command, it is herewith described as new : 



Tyroglyphus heteromorphus n. sp. Plate XVI. Male. — Length, 

 about 0.8 mm.; color, pale white; form, elongated, rounded posteriorly. 

 Tarsi, of first two and fourth pairs of legs, with terminal spme beside 

 the curved claw, no sucker visible, last segment elongated, spiny; an- 

 terior two pairs with two long terminal bristles and with a clavate 

 appendage near the base (fig. 3); posterior pair with but one long 

 terminal bristle and no clavate appendage ; third pair of legs much 

 stouter, tarsi short and bearing several long bristles, terminal hook 

 beak-like and with a short spine opposite (fig. 4). Hairs scattering, equa 

 in length to the abdomen; on posterior margin of cephalo-thorax, two 

 long hairs inclining slightly forward (fig. 2). Posterior to abdominal legs, 

 two suckers may be seen. 



Female (fig. 5). — Slightly longer than male, stouter, abdomen usually 

 much more distended. Tarsi of all the legs much elongated, those of the 

 two anterior pair with a clavate appendage as in the male tut with no 

 short spine beside it (fig. 6) ; legs otherwise similar to those of the male, 

 except that the posterior tarsi bear two long terminal bristles, and that the 

 basal segment of each leg is more nearly globose. Hairs much shorter 

 than in the male, scattering. 



The immature mite resembles the male in general shape. The hairs 

 of the body are not so long and the legs are all similar. The tarsi are not 

 so greatly elongated proportionately as in the anterior legs of the male. 



Hypopus forms. Quite variable not only in size but also in appear- 

 ance, the latter perhaps due to more or less complete transformation. 

 The smaller Hypopus, assumed by immature forms, is suboval from a 

 dorsal aspect, laterally, it appears much flattened and in some examples 

 even concave beneath (fig. 7). The snout or beak projects anteriorly, 

 with parallel margins and is terminated by two long bristles. The ante- 



