CHROMOSOMES OF TIGER BEETLES 439 
The chromosomes of the beetles may be divided into three 
types, depending upon the behavior of the sex elements. 
Type I 
Stevens finds thirty species, ranging through thirteen families, 
which possess an unequal pair of sex-chromosomes (‘hetero- 
chromosomes’). In each case the two members appear united 
on the first spermatocyte spindle, but separate and pass un- 
divided to opposite poles. The union and separation of these 
members vary in different species. In Haltica chalybea (Chry- 
somelidae—Hydrophilidae according to Harvey, 716) the X and 
Y elements are widely separated in prophase and metaphase, 
but come together.in early anaphase and then again separate 
and pass to opposite poles after the autosomes have divided. 
In Doryphora decemlineata and D. clivicolis, X and Y appear 
united in prophase and separate at various points on the spindle. 
Sometimes they seem not to separate at all, but the count in the 
second spermatocyte division shows that they do. In late 
anaphase the larger heterochromosome is often outside the polar 
mass, as is the odd-chromosome in the Orthoptera. 
Wieman (’10) considers that Stevens has erroneously inter- 
preted the behavior of the chromatin material in this form. He 
says: 
The great similarity between the telophase of the first division, as 
represented by Stevens in figures 175 and 176 of her paper, and the 
corresponding stage in L. signaticolis, led me to examine the ovaries 
and testes of D. decemlineata. I.found the nucleolus of the primary 
spermatocytes to accord with Stevens’ description as far as the resting 
stage is concerned, but that its wnequal components separate in the first 
division, does not seem to be the case, and in this regard I cannot agree 
with her observations. 
In Trirhabda virgata the X is larger than the autosomes, 
while the Y is very small. In this case they are closely united 
to a plasmosome. At metaphase they separate and pass to 
opposite poles. In T. canadense, however, the two elements are 
more loosely attached to a plasmosome. In this condition they 
pass about half-way to one pole, then take their position on the 
spindle, and separate before the autosomes divide. 
