316 FOREST ENTOMOLOGY. 



species of this family is often mistaken for a scale — viz., the fringed 

 aphis (Ceyataj)his latanice), known to horticulturists as the " black- 

 seed scale " : it occurs on palms, orchids, &c. (see fig. 292). 



The Psyllidse very much resemble the Aphididae in general appear- 

 ance, but their legs are formed for leaping. The wings are clear, the 

 antennae conspicuous, long, nine- or ten-jointed, and the eyes large and 

 prominent. The tarsus ?s two-jointed. 



In general appearance the Aleyrodidre are the nearest approach 

 to the scale -insects, more especially so in their nymphal or pupal 



stages. Their bodies are of an 

 ivory-white colour, scaly-looking 

 in appearance ; both sexes are 

 winged, and the tarsi two-jointed. 

 ¥\^.im.-sn,Mii.rsn-M^^ Tliey often deposit a scale - like 



secretion on plants (see fig. 293). 

 Aleyrodidc'e are found on tomatoes, &c., in greenhouses, and on ivy, 

 lime, and hazel in the woods. 



The closely allied CocciD^i: are broadly distinguished from the other 

 families of the Homoptera just referred to by the following character- 

 istics — viz. : In the females by being naked (Lecanium), clothed partly 

 with secretion and partly with moulted skins {Diaqnmv), or clothed 

 with white meal-like secretion {Dadylopius), and with Avax-like plates 

 (Orthezia). The tarsus in all the British species but one ^ is composed 

 of a single joint ; there are also two foreign genera in which the tarsi 

 are /^6'O-jointed. 



The larvae are minute, and very active when young, usually naked, 

 and the sexes are inseparable in the first larval stage. 



The female undergoes a semi-complete metamorphosis, is apterous 

 in all stages, has generally a well-developed rostriim, and, according to 

 the genus, the legs may be present or absent. 



The adult male undergoes a complete metamorphosis, and may be 

 winged or apterous. It has no month or feeding-organs, but possesses 

 six legs, eyes, and antennae. 



It is important to bear in mind that both sexes secrete a varying 

 quantity of waxy, horny, mealy, or resinous substances for the forma- 

 tion of their shield-covering or scale, and that these secretions or 

 coverings vary in form and colour. In fact, those differences are so 



1 Excvrdopvs formiriticola, Newst. 



