520 EXTERNAL ANATOMY OF INSECTS. 



they have one. In the genera of both these tribes, the 

 number of joints varies in these organs. Thus, exclu- 

 sive of the seta, in Flata and Cixius there are only ttm 

 joints; in Galgulus, Fulgofa, and Cercopis, there are 

 threes in Lygczus, Coreus, &c. there are four; in Tetyra, 

 Penlatoma, Tettigonia, there are/foe a ; in Aleyrodes there 

 are six ; in Aphis seven; in TJirips eight; in Psylla ten, 

 the last of which is terminated by two bristles b ; and in 

 Coccus eleven. The Neuroptera order, as it stands at 

 present, is regulated by no general rule with regard to 

 the number of joints in the antennas of the insects that 

 compose it. Several types of form in these organs distin- 

 guish its discordant tribes. The frst is that of the Ephe- 

 mera, in which the antennas consist of two short joints, 

 crowned by a short, tapering, unjointed bristle. The second 

 is that of the Libellidina, similar to the above, but with a 

 jointed bristle. The third is that of Psocus, in which the 

 antenna has two short thick joints at the base, terminated 

 by a long filiform bristle, consisting of seven or eight 

 joints, and finer than a hair. Perhaps these three may 

 be regarded as belonging to a common t}>pe. The fourth 

 type is presented by the short filiform antennas of Ter- 

 mes; the fifth by the setaceous ones of Corydalis, Heme- 

 robius, &c; and the sixth and last by the clavate and 

 capitate ones of Myrmeleon and Ascalaphus. In the 

 Lepidoptera and Trichoptera orders the antennae, though 

 varying in their general form in the three tribes of which 

 Linne formed his genera Papilio, Sphinx, and Phalccna, 

 with the exception of Hepialus, in which the joints are 



• l Latreillc says six, but only five arc discernible ; the three last 

 form a kind of bristle. 

 h Latr. Founnis, 323. 



