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On the variation and constancy of the elytral markings 



in Chrysomela, Doryphora and allied genera. 



By C. H. T. Townsend. 



1 have seen some discussion lately concerning the elytral variations 

 of Chrysomela scalaris Lee, aroused by Mr. Angell's interesting notes 

 on the species in a previous number of this journal. I had not intended 

 writing anything on this subject until next season, after having had an 

 opportunity to examine as large a number of specimens as possible dur- 

 ing the summer, but perhaps a few general remarks at the present time 

 on this and one or two allied genera will not be out of place. 



Some interesting notes on a sudden abundance of scalaris have 

 lately been contributed by Dr. Hagen (Can. Entom., vol. XVI, p. 120 

 and 225—6), and some other important observations by Mr. Caulfield 

 (Can. Entom., vol. XVI, p. 226 — 7 and XVII, p. 230). I have never 

 known this species to be abundant in this locality; nearly every season I 

 have taken a few specimens, but no more. I shall find out, whether the 

 species is variable or constant here next season, but allow me to give it 

 as my opinion that if it does not appear in large numbers it will be 

 variable. Mr. Angell, as above referred to, says of scalaris: "Hundreds 

 collected at Cambridge last summer show scarcely any variation, while 

 specimens from New Jersey, Cape Cod and principally Canada are de- 

 cidedly inconstant and variable." This bears out my observations pre- 

 cisely. At Cambridge the species had increased in large numbers and 

 was very constant, while the specimens from other parts of the country, 

 where they had not increased to any extent but were only normally 

 abundant, were very inconstant and variable. This is the point which I 

 wish to bring out. When the species is over-plentiful it seems to be 

 constant, but normally presents many variations. Mr. Caulfield's ob- 

 servations seem to bear me out likewise; from his notes it appears that 

 scalaris is abundant at times in the neighborhood of Montreal, and very 

 constant. Packard states (Bull. U.S. Ent. Com., No. 7, p. 126—7) that 

 in the Summer of 1881 it was very abundant at Brunswick, Maine, on 

 the linden. From specimens taken in July and August he has drawn 

 up descriptions, from which it will readily be seen that the form was ex- 

 tremely constant, and very near the scalaris type. 



A more familiar case to many of us is Doryphora 10-lineata Say, 

 which has become a pest from its abundance, and seems to hold its own 

 as the years roll on. As is well known it shows no variation, but is very 

 constant; it certainly does not vary here (this strip of the country is in- 

 cluded in its original line of most direct spread), and no variations have 

 been noticed to my knowledge in any part of the territory overrun since 

 it began to increase. Specimens taken by me in Lawrence, Kansas, in 



