C. L. Metcalf.
A Malformed Leptinotarsa decemlineata.
Psyche 26:9-10, 1919.

Full text (searchable PDF, 188K)
Durable link: http://psyche.entclub.org/26/26-009.html

The following unprocessed text is extracted from the PDF file, and is likely to be both incomplete and full of errors. Please consult the PDF file for the complete article.

in Drosophila as due to a lagging sex-chromosome. As a full ac-
count of his researches has not yet been published? I am unable to undertake the task of harmonizing it with what I conceive to be the conditions in the Formicidz.
A MALFORMED LEPTINOTARSA DECEMLINEATA.
BY C. L. METCALF,
Ohio State University.
The two accompanying illustrations show an interesting and peculiar malformation of a specimen of the Colorado potato beetle. The specimen was col-
lected by Mrs. Cleo F.Metca1f
at 0ron0~ Maine, August 17,
.1916. It was taken in com-
pany with many normal indi-
viduals feeding upon potato.
Unfortunately its peculiar con-
dition was not noted until it
had been killed, A prolonged
search failed to reveal any
other specimens in any way
abnormal. The chief purpose
in describing it here is to
record for the curious natural-
ist? who does not lack a sense
of humor? a freakish, though
not uncomely, product of one
of nature's sportive moods.
The visible abnormality con-
sists of a deep, V-shaped ex-
cision of each elytron extend-
ing from the apex to about
the basal third of the normal
elytron. The el~tra are a little
Fig. 1. Malformed Leptinoiarsa decem-
foreshortened; the rniddorsal lineaia, showing anomaly in structure and p~ttern of the elytra; below, same in lateral line is nearly straight in side VEW.
About three times natural size.
view; and the usual convexity
covering the tip of the abdomen is entirely wanting, leaving the abdomen exposed from behind.




================================================================================

The two forb of the elytmn formed by the exchion me mqual, the median fork Wig about twice as wide at base and somewhat longer. The labma1 fork is bent sharply wntmhterad and i~ sinuate, its tip esp&lly m h g away from the excision. The apex of the excision is broadly rounded; its sidea are convex inward, The color markings am a.~ little &iturM as could well be-the black mtum md 6ve black stripes on each elflrou being readily recognizable. The kt and second stripes- run nearly their full length. The third runs a little mediad of the apex of the exdsion, shows a slight tendency %KI fork to the outer prong, ad margins the her pmg about halfway to ih q ~ x , ~ a d ~ ~ 1 y attenuating b a point. Its come is such as not to mwwh upon the normal width of the intervening yellow stripe. The mud and third stripes do not, therefore, mite t a d the apex as in the typical individual. The fourth blmk stripe haa a slightly diffemt psition on the two elm. On the left it runs jwt laterad of the apex of the excision margining the outer prong with blwk, within, almost to its apex; gradually mmwing. On the right elytron the fourth stripe cum abmptIy about the millimetem fmm the humerus, eluding the margin of the exusion over its bast1 half, thence hrminating in normal width; after which the margin is again yellow. The fifth stripe m a abut a. normal course, with respect to the margin of the elyimn. This stripe and the yellow hte~vd between it and the fourth stripe are somewhat abnomally widened about mid-]en&. The most notmvodhy featurn of the insect is the vev close mmetry of the two dfomd elytra. Besides the slight dif- ference in the course of the fourth stripe, the only discrepancy is in the Iengkh of the elytm at the suture; the left one excedg the right, by about a half dllimekr.
It is interesting to speculate a~ ta the probable cause of such development. Mere mechanical injwry or pmsure would seem tm be rn inadequate qhnation, unless presumed to occur at a very early stage. The dm similarity of the anomaly hi the two wbga seema t~ me to point tn a deep-seated, physio1ogid distmbauce, the nature of wbkh 1 am entirely mable to mnject~e.~ It is unfortunate that the specimen was nut noted in the to make pmible extensive obmatiom of its behavior, and that an examination of the internal structm of the fresh specimen waa neg1ected. The specimen is in the m~~~tion of the writer.



================================================================================