Coleopterous Fauna of Lower Rio Grande Valley. 83 
gether with larvse. Not unusually abundant; and elytral markings not 
constant, varying more or less in detail. As illustrating a general rule, 
which I announced some fifteen years ago ( Entomologica Americana , 
about 1885), I give below a detailed description of the variations in the 
elytral markings of these nine specimens. This rule is that, in Chryso- 
mela , Leptinotarsa , Doryphora and allied genera, the elytral markings 
vary very considerably when a species is only ordinarily abundant, but are 
very constant during seasons of great abundance or unusual increase of a 
species. 
Color of living adult very pale straw-color ; elytra each with four longi- 
tudinal black lines. Thorax with a varying number of black dots, usually 
five on each side, but sometimes six and again only four; when five, 
arranged in square with fifth in center. Thorax in middle with two 
parallel short longitudinal lines, these lines sometimes broken up into 
four spots and sometimes united posteriorly into a Y-shaped marking. 
Head with three constant spots. Scutellum narrowly or broadly mar- 
gined with black, or wholly so with only faint lighter area in middle. 
Two outer elytral stripes generally joined behind in acute angle, espe- 
cially in the more robust specimens; sometimes the inner of the two 
abbreviated behind and not joining outer one. Inner stripe of inner pair 
always shorter than outer one of same pair; the inner one much more 
shortened behind in some specimens than in others. Narrow inner edges 
of elytra posteriorly black for a greater or less extent. When inner line 
of outer pair is abbreviated behind, its extreme end is left in conjunction 
with end of outer line, forming a hook, or is sometimes represented by 
only a dot separated from end of outer line, the latter being the case 
when the outer line shows a tendency to become faint posteriorly. Pro- 
thorax with a longitudinally elongate black dot below on each side; meso- 
thorax below with a longitudinally narrow straight distinct thread-like 
black line on each side, pointing outward a little behind, and a spot more 
or less triangular outside its anterior end. Yenter with two spots on last 
segment, and two in middle and one on each side of other segments. 
Although the larva has been described and figured by Duges (Ann. 
Soc. Ent. Belg., XXYIII, 1884), I, nevertheless, append the following 
description, made from two living larvae taken with the above nine adults, 
which will form a contribution to a knowledge of the variation of the 
markings in the larval stage. 
Larva. — Length, seven to nine or ten mm., according to whether they 
are crawling undisturbed or contracted in length on being disturbed; 
width, six to seven mm., according to same conditions. Color, pale, dilute 
yellowish, or pale straw color. Head pronounced brownish-vellow. Pro- 
thorax evenly and narrowly margined with shining black, only widened 
in a slight cloud in middle of hind margin in one specimen. Mesothorax 
