308 
Psyche 
[December 
Since 1921, however, electa has become a serious pest of peppers and 
eggplants in the eastern United States. Recently it was found attack- 
ing these plants as far north as southwestern Ontario (Foott 1963). 
The hosts of the three new species are not known, but they may also 
be expected to infest the fruits of solanaceous plants. 
There is evidence that the pepper and horsenettle populations, at 
least in Ontario, have become somewhat ecologically isolated from 
each other. Foott (1963) noted that larvae from horsenettle emerge 
later and are considerably smaller than those emerging from peppers. 
He offered three possible explanations for this observation : micro- 
climatic conditions were different for the two hosts; nutritive quali- 
ties of the fruits varied ; earlier availability of pepper fruits allowed 
expansion of the early emerging fly population. As pointed out by 
Bush (1966), the third possibility would establish allochronically 
isolated populations on different hosts and permit divergence to prog- 
ress rapidly in the absence of gene flow from the parent population. 
This could result in the formation of two distinct host races. A 
careful study of these populations would be extremely interesting as 
little is known about the formation of host races and species in 
phytophagous insects. 
CYTOLOGY 
Mitotic configurations in the larval brain and adult testes were 
examined in Z. electa and Z. vittigera. Tissue was pretreated in a 
saturated aqueous solution of coumarin for 5-8 minutes, fixed and 
stained in proprionic orcein for 5 minutes, and squashed in a drop 
of stain following the method of Bush (1962). Pretreatment of the 
tissue with coumarin was necessary to produce well flattened meta- 
phase plates and to locate the kinetichores. 
The karyotypes of both species are indistinguishable. In the 
male there are five pairs of very small metakinetic autosomes 
and a heteromorphie pair of extremely long acrokinetic and hetero- 
chromatic sex chromosomes (Fig. 1). Following coumarin pretreat- 
ment the chromatids of the X chromosome at metaphase are usually 
joined only at their extreme ends forming an oblong ring (Fig. 1, 
X). The chromatids of the shorter Y chromosome are usually 
closely approximated over much of their length and form a figure 
Explanation of Plate 22 
Figs. 1-3. Mitosis in neuroblast cells of Zonosemata electa: (1) meta- 
phase; (2) prophase; (3) anaphase. 
Figs. 4-8. Right wings of Zonosemata spp.: (4) electa, N. J., U. S. A.; 
(5) vittigera, Texas, U. S. A.; (6) cocoyoc, paratype, Morelos, Mex. ; 
(7) mlnuta, type, Jamaica, W. I.; (8) vidrapennis, paratype, Mexico, Mex. 
