Microscopical Essays, 



It is called obtecta, difguifed or fhrowded, when the infect is 

 enveloped in a cruftaceous covering, confiding of two parts, one 

 of which furrounds the head and thorax, the -other the abdomen, 



It is termed incompleta, when the pupa has perceptible 

 wings and feet, but cannot move them. 



Semicompleta ; thefe can walk or run, but have only the 

 Tiidiments of wings. The difference between the pupa and the 

 larva of this cla'fs is very inconfiderable, as they eat, walk, and 

 aft, juft as they did in their primitive ftate ; the only remarkable 

 difference is a kind of cafe, which -contains the wings that are to 

 be developed in their fly ftate. 



'Completa; thofe defigned by this name take their perfect 

 form at their birth, and do not pafs, like other infe&s, through 

 a variety of ftates, though they often change their fkin. 



It is a general rule, that all winged infecls pafs through the 

 larva and pupa ftate before they aftume their perfect form ; there 

 are alfo infecls which have no wings, and yet undergo fimilar 

 transformation, as the bed bug, the flea, &c. Other infecls, 

 which have no wings, and which always remain without them, 

 never pafs through the pupa ftate, but are fubjecl to conliderable 

 changes, as well with refpeclto the number as the figure of their 

 parts ; thus mites have four pair of feet, and two fmaller ones at 

 the fore part of the body, near the head yet fome of thefe are 

 born with only three pair of feet, the fourth is not perceived til 

 fome time after their b>irth.* The figure of the monoculus 



quadri- 



* De Geer Memoires pour fervir a PHiftoire des Ink&cs, torn. i. p. 154. 



