8 BRITISH APHIDES. 
orders Heteroptera and Homoptera. Aphides pertain 
to this latter group, inasmucli as, of the four mem- 
branaceous wings which they possess, the two upper 
want the semicoriaceous portions which distinguish 
the wings of the Hemiptera proper. 
Although Linnaeus places Aphides between the 
Cirnicidse and Chermesidse in his system, they seem to 
be more closely connected with the Coccidse on the one 
side, and the Psyllidse on the other. They also hold 
many characters in common with the more distantly 
related Cicadiid^ or froghoppers. Aphides differ, 
however, from the Ooccidge in being of a more active 
habit, and from the Cicadidse in being quite incapable 
of leaping, and possessing besides antennse of a different 
character. By these last attributes also, they may be 
distinguished from the Psyllidge or leaping plant-lice. 
Perhaps of all insects in this group, the Aphides are 
the most difficult to describe. Linnaous says, before 
giving his remarks on the thirty-three species which 
came under his notice, Species difficile distinguntur, 
difScilius defininntur, nec semper in diver sis plantis 
diversse species, adeoque pauciores mihi aphides quam 
plantae aphidiferae.” 
Thanks to the labours of Burmeister, von Heyden, 
Kaltenbach, Koch, and Passerini, the family now has 
been cut up into genera, with more or less success ; 
which procedure has much facilitated its study. 
Without closely following these three last systematic 
authors, an endeavour has been made rather to har- 
monise their schemes, which have so much in common, 
than to introduce confusion into a subject, already 
sufficiently intricate. 
Partly for this reason, neither the classification so 
elaborately set forth by Sign or et in his regrouping of 
the Phynchota, nor the system of Schiodte, which is 
founded upon the form and rotation of the cox80, has 
been adopted.'^ Difficulties, it must be confessed, as 
to the true natural classification of Aphides still remain. 
Signoret, ‘ An. Soc. Ent. de France/ 4® ser., t. ix, pp, 549-596. 
