252 . Acarology 



yet been carefully surveyed for these mites. As a conservative estimate 

 then, there are at least several thousand species of trombidiids, most 

 of which await description. 



Trombidiids are world-wide in distribution and have been found 

 on every major land mass except those covered by ice and snow the 

 year around. They are more abundant in the tropics than in temperate 

 climes and are a conspicuous portion of the mite faunas found on 

 oceanic islands. 



The life history of trombidiid mites is as follows: egg, deutovum, 

 larva, nymphochrysahs, nymph, imagochrysalis, imago. The life cycle 

 of Eutrombidiiim rostratus has been well worked out by Severin 1944. 

 Michener 1946 has found that microtrombidiids may undergo several 

 postimaginal molts. The sex ratio is 1 : 1 in the cases investigated. The 

 penis of the males will serve to distinguish them from females. 



Trombidiid larvae parasitize arthropods and because of this habit 

 they may potentially be important not only in the control of arthropods 

 but also in the transmission of micro-organisms from one arthropod 

 to another. The nymphal and adult stages feed on the eggs and early 

 larval instars of many arthropods, and thus aid in keeping down their 

 numbers. Eutrombidiiim rostratus is an important enemy of the locust. 

 Its larvae feed on the locusts and its adults feed on the eggs of locusts. 



References: 



Berlese, A. 1912. Tromb|diidae. Redia 8:1-291. 



Feider, Z. 1950. Cercetari asupra aparatului respirator la Trombidiidae 

 si prostigmatele superioare si lista speciilor de Trombidiidae din Re- 

 publica Populara Romana. Ann. Acad. Repub. Pop. Romane, Vol. 

 3, mem. 5:1-185, Pis. 1-21. 



Michener, C. D. 1946. The taxonomy and bionomics of some Panamanian 

 trombidiid mites (Acarina). Ann. Ent. Soc. Amer. 39:349-380. 



Severin, H. C. 1944. The grasshopper mite Eutrombidium trigoniun (Her- 

 mann) an important enemy of grasshoppers. S. Dak. Agr. Expt. Sta. 

 Tech. Bull. 3:1-36. 



Thor, S., and C. Willmann. 1947. Trombidiidae. Das Tierreich Lfg. 71b: 

 187-541 + Pis. XXIX-XXXVI. 



Womersley, H. 1945. A revision of the Microtrombidiinae (Acarina, 

 Trombidiidae) of Austraha and New Guinea. Rec. South Austral. 

 Mus. 8:293-355. 



