16 BULLETIN 826, U. S. DEPARTMENT OF AGRICULTURE. 



The following type fixations have been made for JLachnus: 



1840. Aphis roboris Linnaeus, Westwood. 



1863. Lachnus piniceila Kaltenbach, Passerini. 



190S. Aphis nudus De Geer, Mordwilko. 



1910. Lachnus punctatus Burmeister, "Wilson. 



1911. Lachnus fasciatus Burmeister, Wilson. 



Now the first three fixations are invalid, since the species were 

 not included in the original genus. The first valid fixation, there- 

 fore, is that of Wilson, 1910, when he set punctatus as type. This 

 fixation, according to present rules, can not be changed in 1911 

 because it is an unfortunate fixation, but punctatus must remain 

 the type of the genus Lachnus. The question is now purely zoo- 

 logical. At present punctatus is unknown and, therefore, the genus 

 Lachnus must remain unknown until punctatus is discovered. This 

 is the situation, if the rules are followed, and the well-known genus 

 name will be lost to us. At the suggestion of numerous aphid workers 

 we are holding fasciatus as the type of Lachnus and the Commission 

 will be asked to suspend the rules hi this case on account of the long 

 usage of the name Lachnus. 



In 1909 Del Guercio erected the genus Lachnielia without setting 

 a type but in 1911 Wilson interpreted this genus as Lachnus with 

 fasciatus Burro. . as type. Following this the writer definitely desig- 

 nated this species as type. Therefore, Lachnielia will become a syno- 

 nym of Lachnus. 



Characters. — Eyes large, "with distinct ocular tubercles present. Antennae of six 

 segments and with rather prominent hairs. Cornicles on somewhat shallow hairy 

 cones. Fore wings with the radial sector short and straight ; stigma elongate; media once 

 branched. Labium lance-like. 



Type (by suspension of rules), fasciatus Burnt. 



Genus DILACHNUS Baker. 



Plate II, A-C. 



1919. Wilsonia Baker, Can. Ent., v. 51, p. 212. 

 1919. Dilachnus Baker, Can. Ent., v. 51, p. 253. 



Characters .—'Eyes with distinct ocular tubercles. Antennae of six segments and 

 armed with slender hairs and circular sensoria. Cornicles on rather broad hairy cones. 

 Fore wings with radial sector straight, media twice branched ; hind wings with both 

 media and cubitus present. 



Type (fixed by Baker, 1919), Lachnielia gracilis Wlsn. 



Genus SCHIZOLACHNUS Mordwilko. 

 Plate II, D. 

 190S. Schizolachnus Mordwilko, Ann. Mus. Zool. l'Acad. Imp. des ScL, St. Petersbourg, v. 13, p. 375. 



The genus Schizolachnus was erected by Mordwilko with tomen- 

 tosus De Geer {pineti Fab.) as type. 



Characters. — Eyes large and with ocular tubercles present. Antennee of six seg- 

 ments and with rather prominent hairs. Cornicles on somewhat shallow hairy cones. 

 Fore wings with the radial sector straight; stigma elongate; media once branched. 

 Labium obtuse. 



Type (fixed by Mordwilko, 1908), Aphis tomentosus Be Geer. 



