CRUST ACEOLOGY. 



415 



Arachui- 

 dcs. 





17. ACA- 

 RUS. 



Siro. 



Farinar. 



r8. Ombi. 

 ri. 



iemcu- 



Ua. 



rhelepro; 

 us. 



assidea. 



.lata. 



Sp. S. Reticulates. Bright blood red beneath, above 

 whitish, variegated, with brownish blood colour ; the 

 dorsal marks obscurely marginated ; the sides of the 

 abdomen marginated, punctated, and striated; palpi 

 somewhat oval. 



Acartts reticulalus, Fabr. 



Acarus reduvius, Schrank. 



Ixodes reticulalus, Latr. 



Inhabits various plants; is very common in Genista;; 

 it fixes itself to oxen. When its abdomen is distended, 

 it is nearly five lines in length, and is then of an ash 

 or pale yellow colour. 



Family VII. Acarides. 



I. Palpi very short, not exserted. 



Genus XVII. Acarus, Linn. Geoff. De Geer. Fabr. 

 Oliv. Hermann. 



Body soft ; parts of the mouth naked. 



Tarsi with a pedunculated vesical at the apex. 



Sp. 1. Siro. Whitish, with two brown spots ; body 

 oval, contracted in the middle, with very long hairs ; 

 feet equal in length. 



Acarus siro, Linn. Fabr. 



Ciron dufromage, Geoff. 



Acarus domesticus, Latr. 



Inhabits cheese and flour too long kept. Is called 

 cheese-mite, and much esteemed by most people, who 

 say it heightens and improves the flavour of cheese. 

 Latreille supposes Acarus dimidiatus of Hermann may 

 be this species. 



Sp. 2. Farina. Oblong and white ; head reddish ; 

 feet conical, thicker, and of an equal length. 



Acarus farina;, Schrank, Latreille. 



Acarus favor urn, Hermann ? 



Observe. Are Acarus lachis and Dysenteries, of 

 Linne and Fabricius, distinct from Acarus farince of 

 Latreille? They are probably merely the young of 

 that species. 



Genus XVIII. Oribita, Latr. Acarus, Linn. Fabr. 

 Oliv. Geqf. Notaspis, Her. 



Body with a coriaceous covering, (back generally 

 shielded,) rostrated before ; the rostrum including the 

 parts of the mouth. 



Tarsi, generally with three nails at their extremi- 

 ties. 



* Abdomen somewhat globose, neither angulated in 

 front, nor furnished with wing-like processes. 



Sp. 1. Geniculata. Brownish red, shining and hairy ; 

 feet pale-brown ; thighs rather clubbed. 



Acarus geniculatus. Linn. 



Oribita geniadata. Latreille. 



Inhabits trees and stones in various parts of Europe. 



Sp. 2. Theleprocius. Black; back clypeated; the 

 shield divided and striated by concentric circles. 



Notaspis theleprocius. Hermann. 



Oribita thcleproctus. Latreille. 



Inhabits France and Scotland. Its form is that of a 

 shield, its motion very slow. 



Sp. 3. Cassidea. Brownish-red ; scutum depressed 

 and transparent; anterior feet antennae-Eke. 



Notaspis cassidea. Herm. 



Oribita cassidea. Latr. 



Inhabits mosses. Is found in France and Britain ; 

 in the latter country it is very common. 



** Abdomen somewhat globose ; the anterior margin 

 produced into an angle, or wing-like process. 



Sp. 4. Alata. Abdomen very smooth ; obscurely 

 brownish red ; the sides with wing-like processes. 



Tegeocra- 

 Da. 



19. Gam a . 



SUS. 



Coleoptra- 

 torum. 



Acarus adcoplralus. Linn. 



Oribita alata. Latr. 



Nolaspis alata. Herm. 



Inhabits mosses. 



Sp. 5. Humeralis. Abdomen blackish-brown-red, Humeralis 

 and very smooth ; the sides produced into a straight 

 angular membranaceous process. 



Notaspis Humeralis. Herm. 



Oribita Humeralis. Latr. 



*** j} d omen somewhat quadrate, neither angulated 

 nor winged. 



Sp. 6. Tegeocrana. Abdomen oblong ; the anterior 

 margin with four white setse ; the head covered by a 

 triangular scutum ; the lateral squamula pellucid. 



Notaspis tegeocrana. Herm. 



Oribita tegeocrana. Latr. 



Inhabits mosses. 



Sp. 7. Horrida. Body rough ; abdomen with two Horrida 

 teeth behind, and four hooked processes. 



Notaspis horrida. Hermann. 



Oribita horrida. Latreille. 



Inhabits mosses. In this country it appears to be 

 very rare, having been found but once in a wood in Nor- 

 folk, near Cossey, by Mr Leach. 



I. Palpi exerted and prominent. 



A. No moveable appendage at the extremity of the 

 palpi. 



Genus XIX. Gamasus, Latr. Acarus, Linn. Fabr. 

 Oliv. Herm. Trombidium, Herm. 



Pulvilh vesicular at the apex of the tarsi. 



* Body depressed ; the whole, or part of the skin 

 of the back, coriaceous. 



Sp. I. Cokoptratorum. The anterior part of the 

 back, and a triangular spot behind, coriaceous and fus- 

 cous; the anterior and posterior pair of feet rather 

 longer than the rest. 



Acarus coleoptralorum. Linn. Fabr. Donovan. Herm. 



Gamasus coleoptralorum. Latr. 



Inhabits the dung of oxen and horses, attaching it- 

 self to such coleopterous insects as come there to feed 

 or deposit their eggs. We have frequently seen Geo- 

 trupes stercorarius, (the common clock, or dor beetle,) 

 and Necrophorus vespilo and Immator, (grave-digging 

 beetles.) nearly covered by hundreds of these animals. 



Sp. 2. Marginatus. Oval, brown, and hairy ; cori 

 aceous above and below ; the sides of the abdomen be- 

 ing alone membranaceous and white ; the anterior feet 

 nearly twice as long as the rest. 



Acarus marginatus. Hermann. 



Gamosus marginatus. Latreille. 



Inhabits dung and putrescent plants, where it fre- 

 quently occurs. Latreille supposes acarus cellaris of 

 Dr Hermann is the same insect ; it differs, however, in 

 having very unequal feet, and an immarginate body ; 

 if his figure therefore be correct, it is a distinct species. 



Sp. 3. Crassipes. Second pair of feet very thick and Crassipes, 

 toothed. 



Acarus crassipes. Hermann. 



Gammasus crassipes. Leach's MSS. 



Obs. To this family, acarus testudinarius of Hermann, 

 (tab. 9- fig- L) and acarus longipes, (tab. 1. fig. 8.) of 

 the same author appear to belong ; but as we have 

 never seen the animals, we cannot be too cautious in 

 giving our opinion. 



** Body with a soft skin, back not coriaceous. 



Obs. We are unacquainted with all the members com- 

 posing this family ; and shall therefore give Latreille's 

 ideas on the species which he supposes to belong to it. 

 " Some few of the Tuombidja and Acari of Hermann 



Margins 

 tus, 



