HOMOPTERA. — APHID. 437 
like manner illustrated Ps. Pyri, Urticee, and Betulz, the last of which 
in the larva state is densely enveloped in a cottony secretion. Two 
species, Psylla Pyri and Chermes Mali Schmidberger, are very in- 
jurious in orchards, the former to the young shoots and leaves of the 
pear, and the latter to the apple. The history of these two species 
is given in Kollar’s Treatise on Insects injurious to Gardens, &c. 
translation, p. 275—284.; and some particulars relative to the pear 
Psylla were published by Mr. Knight in Hort. Trans. 2d series, vol. ii. 
p- 107.; and Gard. Mag. (Loudon) No. 92., Nov. 1837. Latreille has 
given us the history of a curious species, Livia Juncorum, which in- 
habits the common Juncus articulatus, depositing its eggs in the 
flowers, or at least in their shoots: the action of the sap produced a 
monstrosity in the diseased part, resembling a bundle of grass, within 
which the insects reside in their different states, supporting them- 
selves on the juice of the plant, and emitting a white farinaceous ex- 
crementitious secretion, in the midst of which they delight to reside. 
(Bull. Soc. Philomat. tom. i., and Hist. Nat. Fourmis, p. 325.) Mr. 
Curtis has figured this insect (Brit. Ent. pl. 492.), and has stated that 
he detected three joints in the tarsi; the basal joint being, however, 
scarcely visible, except in the hind legs. 

The family Apu1tp%* comprises the very numerous and obnoxious 
species of plant lice (jig. 117. 10. Aphis Persicz), a tribe of insects 
* Bretiocr, Rerer. tro tHE APrHiIp&. 
De la Hire. Obs. sur 1. Pucerons, in Mém. Acad. Se. Paris, 1703. 
Bonnet. On Aphides, in his CEuyres, tom. i. 
Richardson. Obs. on the Aphides of Linnzus, in Phil, Trans. 1771. 
Bjerkander, in Swed, Trans. 1784. 
Hausmann. Beitr. d. g. d. Blattiause, in Viger. Magaz. zu Insekt. b. 2. 1802. 
Kyber. On ditto, in Germar’s Magazin d. Ent. 1812. 
Dutrochet. Anat. Aphides, in Annales des Sci. Nat., Oct. 1833. 
Duvau. Nouv. Rech. sur l’Hist. n. de Pucerons, in Mém. Mus. d’Hist. Nat. 
tom. xiil. 1825, and Ann. Sc. Nat. tom. v. 
Kittel, in Ann. Soc. Linn. de Paris, tom. v. 
Boyer de Fonscolombe, in Ann. Soc. Ent. de France, tom. iii. (Phylloxera. ) 
Haliday, in Annals of Natural History, Nov. 1838. 
Ferussac. Puceron de Therebinth, A. Pistacia, in Nouv. Bull. de Sci. tom. ili. ; 
and in Bull. Soe. Phil., 1812, 1813. 
Macquart. Puceron du Blé, in Ann. Sci. Nat., April 1831, 
‘e) 
FF 6 
