16 BULLETIN 826, U. S. DEPARTMENT OF AGRICULTURE. 
The following type fixations have been made for Lachnus: 
1840. Aphis roboris Linnaeus, West wood. 
1863. Lachnus pinicola Kaltenbach, Passerini. 
1908. 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 he 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 in this case on account of the long 
usage of the name Lachnus. 
In 1909 Del Guercio erected the genus Lachniella without setting 
a type but in 1911 Wilson interpreted this genus as Lachnus with 
fasciatus Burm. as type. Following this the writer definitely desig- 
nated this species as type. Therefore, Lachniella 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 Burm. 
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), Lachniella gracilis Wlsn. 
Genus SCHIZOLACHNUS Mordwilko. 
Plate II, D. 
1908. Schizolachnus Mordwilko, Ann. Mus. Zool. l'Acad. Imp. des Sci., 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. Antenme 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 De Geer. 
