224 ZOOLOGY. 



nerally deposited on the skins of some other animal, f*rom 

 these in a short time the larva; are hatched, which are desti- 

 tute of feet ; of a lengthened form, and thickly beset with 

 hair ; their lar /ae are often found in the nests of birds, attach- 

 ed to the young brood, on the juices of which they feed ; in 

 a few days they arrive at fu'J growth, and then change into 

 the chrysalis state, the pupa is enveloped in a cotton like 

 case, these remain a longer or shorter time in this state, ac- 

 cording to the season of the year, in warm weather about 

 twelve days is the usual time ; when the perfect insect is 

 then developed. 



5. Acarus. Mite. Palpi two jointed, shaped like the 



legs ; eyes two, situated on each side of the head ; legs 

 eight. 



The larger number of the Acari, are amongst the most 

 minute of the insect tribes, they feed on various substances, 

 but mostly on those in a state of decay ; some of the larger 

 kinds, as that well known insect the Tick, live on the juices 

 of other animals ; so numerous is this tribe, that perhaps it 

 is not too much, io say, that, almost every animal has 

 some one peculiar to the species. 



6. Hydrachna. Head, thorax, and abdomen united 5 feel- 



ers two, jointed ; eyes two, four, or six; legs eight, 

 ciliate, formed for swimming. 



An aquatic genus, feeding on the larvae of various other 

 aquatic insects. 



