74 BRITISH APHIDES. 



it probable that he mistook this insect for Lachnus 

 fasciatus. As I consider this last to be of a different 

 species, I altogether exclude it from the synonyms 

 above written. 



The reader is referred to a paper by M. Lichten- 

 stein,* in which he says that he watched the ma- 

 noeuvres of eight males, which discovered several cap- 

 tive females through some instinct which he could not 

 explain. These males eventually coupled with about 

 one hundred females, which soon disposed themselves 

 to lay their eggs. These eggs formed a crust of great 

 regularity, and were covered by a brilliant black 

 varnish. Sometimes they have also, he remarks, a 

 covering of downy matter. The eggs bear with 

 impunity a temperature of 12° or 15° below zero 

 Centigrade. 



Thus, unlike most insects, polygamy is practised by 

 the males of Aphis. M. Lichtenstein tells me that he 

 has often seen the winged males waiting for the females 

 which gather on the same tree, which, after fecunda- 

 tion, place their eggs in a wonderful order on the same 

 branch. In the case of Dryobius roborls " a branch 

 may be covered for a foot or more." 



Dryobius croatious, Koch. Plate CIV. 

 ApJiis Tohoris, Walk. 



Apte7vus vivijjarous female. 



Inch. Millimetres. 



Size of body 0-150 X 0-080 3-81 X 2-02. 



Length of antennae 0-070 1*77. 



"O 



55 



55 



cornicles 0-010 0*25. 



rostrum 0-100 2-54. 



"Very large. Head and thorax rather narrow. Ab- 

 domen broad across the nectaries. Greneral colour 

 isabel-brown, passing into a redder shade; head 

 * 'Bull. Soc, Ent. de France' (5), iv, pp. 241, 242. 



