20 
general appearance to the full-grown insect, and it is somewhat diffi¬ 
cult to distinguish it from the lull grown wingless individuals. 
Pupa .—This term is usually applied only to that stage of the winged 
individuals, during which the embryo wings appear like little scales at 
the sides. As these insects never go into the quiescent or apparently 
lifeless state of the true chrysalids of the beetles and butterflies, the 
wingless specimens have no marked or readily distinguished pupa state, 
and hence this term is seldom applied to them. 
Imago .—The perfect insect, or the individual which has passed 
through all its moultings and has acquired its full growth, whether 
winged or wingless. In the plant-lice the large majority never acquire 
wings, but remain feeding during their short period of existence on or 
near the particular spot where they are born. 
On account of their singular method of reproduction, which will 
hereafter be explained, it has been necessary to introduce additional 
terms for the various forms of the different sexes. r llie male, so far 
as yet known, assumes but one form in species, (except possibly in 
some species subject to dimorphism or polymorphism, terms which 
will be explained hereafter) ; the females*, however, present such marked 
differences in their habits that it is necessary to distinguish them. 
Some are winged while others are apterous ; some produce only living 
young while others produce only eggs. 
The male as a general thing, in fact almost universally, h winged; 
exceptions are to be found undoubtedly in those species which never 
acquire wings; one or two European Entomologists think they have 
in a few' instances observed wingless males in species where some 
individuals acquire these organs. 
Winged viviparous females : A w'inged female wdiich produces only- 
living young. 
'Apterous or wingless viviparous female: 
produces only living young. 
Apterous or wingless oviparous female : 
produces only eggs. 
A wingless female which 
| 
A wdngless female which 
The term winged oviparous female is not used, as up to this time 
few instances have been found where the oviparous individuals were 
winged, and these only in the lower types, where as will be shown 
hereafter, the method of reproduction is only oviparous. 
Agamic .—Is a term which is applied to 
individuals which produce young without the 
Agamic female is not precisely equivalent 
though the latter is agamic , it applies to 
those females or asexual 
intervention of the male, 
to oviparous female; al- 
reproduction without the 
intervention of the male whether it be viviparous or oviparous. 
External Anatomy. 
The external integument or sk'n which 
as the basis for the attachment of muscle 
leathery as in most other insects, is soft 
forms the skeleton and acts 
s, instead of being rigid or 
and yielding, rendering the 
