42 



REPORT 108, U. S. DEPARTMENT OF AGRICULTURE. 



at or near tip. There is uo proof tliat these are homologous with the organs of the 

 same name in the Oribatidse, although it is possible. Sometimes these organs are 

 present, although the crista is absent, and in one species there are two pairs of the 

 organs. The function of these organs is entirely unknown. The genital aperture is 

 situated between the hind coxae; the anal opening is smaller than the genital and 

 placed a little behind it. 



The larvae (figs. 65, 66, 67) are six-legged mites and parasitic on various insects. 

 They, with other larval forms, were formerly supposed to be adult and to constitute 

 a distinct family under the name of Microphthiridae. Three of the genera of that 

 family, Leptus, Oq/petus, and Atoma (or Astoma), are now known to be larval Trom 



Fig. 63. 



-Leg I of Trombidium. (Author's 

 illustration.) 



Fig. 64.— Mandible of Trombidium: p, Tra- 

 cheal pores; <, trachea. (Author'.s illustra- 

 tion.) 



bidiids. Some of these larvae are, in certain localities, very numerous, and will attach 

 themselves to man, causing intense itching, soreness, and even more serious compli- 

 cations. They have received the popular name of ''red bug." In parts of the South- 

 em States the ''red bugs" are often a source of great annoyance. They enter pores of 

 the skin and produce inflamed spots. It is an unnatural situation for the mites and 

 they soon die, but the waiting is not pleasant. They can be killed by anointing the 

 affected spots with an ointment or salve containing sulphur. Some recommend 

 sponging with a weak solution of carbolic acid (an ounce to a quart of water) after a 

 soap bath. Allied species occur in all warm countries and ha^•e become obnoxious 



enough to receive a popular name. In France, 

 where they are often very troublesome, they arc 

 called "rouget" or ''aoutat," and are the cause 

 of "erythema autumnale.'' In parts of Scot- 

 land it is called ''berry bug." In parts of Ger- 

 many a severe infestation is known as "stachel- 

 l)eerkrankheit." In England it is called the 

 •'harvest mite" and ''gooseberry bug." In 

 Mexico red bugs are known as ''tlalsahuate," 

 in Japan as ''akamushi." and in parts of the 

 West Indies as the "bete-rouge." In Celebes 

 they are known as the 'gonone," in parts of 

 New Guinea as the ''arkan," and in Guiana are 

 called ''batata mite." In Japan they are con- 

 sidered by some to transmit the "kedani" dis- 

 ease, or river fever, but the evidence is not as yet 

 conclusive. In all those countries they have at times been a serious annoyance to the 

 pea.santry and hindered or prevented the harvesting of certain crops. The "red bug" 

 is not the larva of only one species of Trombidium, l)ut of several species; in each lo- 

 cality there are apt to be two or three forms of "red V)ug." In France Bruyant has 

 shown there are at least three forms of ''red bug," one of which is the larva of Trom- 

 bidium inopinalum Oudemans, another the larva of T. holoscriccum Linn., while the 

 adult of the third form is unknown. Evans hiis found that the larvae of the European 

 T. holosericeum will not attack man; doul)tless they feed on insects or small mammals. 

 The female Trombidium (fig. 7, p. 13) deposits her eggs in or upon the ground, some- 

 times as many as 400 together. They are usually brown and spherical, and were ])y 

 some early writers considered to be fungi. The outer skin or chorion soon splits. 



Fig. 



05.— The larva (leptus) of a Trom- 

 bidium. (Author's illustration.) 



