INSECTS 



TETTIGONID.* (continued) 

 Evacanthus interruptus, L. 

 Tcttigonia, Geoff. 



viridus, L. 



ACOCEPHALIDVK 



Acocephalus, Germ. 



nervosus, Schr. 



albifrons, L. 

 Eupelix, Germ. 



cuspidata, Fabr. 

 JASSID/E 



Allygus, Fieb. 



commutatus, Fieb. 



modestus, Fieb. 

 - mixtus, Fab. 



Thamnotettix, Zett. 



dilutior, Kbm. 



subfuscula, Fall. 



(continued) 

 Thamnotettix crocea, H.S. 

 TYPHLOCYBID.W 

 Alebra, Fieb. 



- albostriella, Fall. 

 Chlorita, Fieb. 



flavescens, Fabr. 

 Eupteryx, Curt. 



vittatus, L. 



urticze, Fabr. 



- pulchellus, Fall. 



PSYLLINA 



PSYLLID.* 



Psylla, F. Low 



alni, L. 

 Arytaena, Scott 



genistz, Latr. 



APHIDES 



Plant Lice 



Although dwellers in the country are necessarily much too familiar 

 with the insects included in this section, nobody seems to have system- 

 atically studied and differentiated the Essex species. 



Of all insects they are the most numerous, the most ubiquitous and 

 the most harmful, and the loss they sometimes occasion is incalculable. 

 They infest alike the lowliest herbage and the loftiest trees ; some live 

 underground upon roots, out of which they suck the sap, and others 

 submerged in water upon aquatic plants. In former times it was 

 imagined that every plant had its own peculiar Aphis, and as the various 

 species were named after the plants upon which they were found some 

 of them received a large number of names, which are sunk as synonyms 

 now that we know that the same Aphis in some cases affects a great 

 many different plants, and that some of these afford sustenance to several 

 different Aphides. 



When they first appear in the spring they are not very numerous, 

 but they arrive at maturity so rapidly, and increase at such a prodigious 

 rate, that before the summer is far advanced it is said a single individual 

 may number its descendants by hundreds of millions, and the term 

 ' Smother-flies,' which is sometimes applied to them, is then amply 

 justified. Their life history is very interesting and peculiar, for the 

 ordinary processes of nature have been so materially modified to meet 

 their special case that the actual facts would appear almost incredible if 

 they had not been abundantly proved. The first brood of the year 

 emerges from eggs which have been laid by the fertilized females of 

 the previous autumn, and consists of females exclusively, which without 

 any male intervention bring forth other females, and the process is con- 

 tinued as long as a suitable food supply lasts and the climatic conditions 

 remain favourable ; but when these change a bisexual brood is produced, 

 the males of which fertilize the females, and eggs are deposited which 



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