CRYPTIC SLEEPING POSTURE OF 
A SKIPPER BUTTERFLY, ERYNNIS BRIZO* 
By John M. Burns 
Museum of Comparative Zoology, Harvard University 
Hesperiids have seldom been observed asleep in nature. A major 
exception to this general statement is provided by the hesperiine 
Thymelicus lineola ( Ochsenheimer) , an early twentieth century 
accidental import from Eurasia now thriving in much of its expand- 
ing North American range (Arthur 1966; Burns 1966). The ex- 
traordinarily high density attained by colonizing populations of T. 
lineola has drawn attention even to dormant individuals. Hensel 
(1966) found numerous examples clinging to vegetation in early 
evening at Edmundston, New Brunswick, and easily sampled them by 
hand. I similarly sampled T. lineola on the evening of 24 June 
1968 in a pasture at Durham, Middlesex County, Connecticut, 
where it abounded, although it had begun to appear in that region 
only five years before (Apter and Burns 1965). The sleeping 
skippers sat exposed on leaves, stems, and flowers of forbs and 
grasses, with the upper sides of the wings together above the back — 
a position commonly assumed by these skippers when momentarily 
at rest in the course of diurnal activity. There was no suggestion 
of concealing behavior. 
In contrast to this are two observations on a native pyrgine, 
Erynnis brizo (Boisduval and Leconte), made when I was collecting 
genitalic differentiates of this species, and natural hybrids between 
them, in Texas (Burns and Gillmor, in preparation). E. brizo 
characteristically rests between diurnal flights with both pairs of 
wings stretched out horizontally. 
In pine and scrubby oak habitat along park road Pi between 
Bastrop and Buescher state parks, Bastrop County, Texas, on 14 
March 1967, at 1730 hours C.S.T., a flying E. brizo brizo male 
that I was pursuing abruptly flew to a dead branch on the prostrate 
skeleton of a shrub. The gray, barkless branch was about the diam- 
eter of a, lead pencil, about half a meter above the ground, and 
parallel to it. The skipper lit on the ventral side of this branch 
and instantly embraced it by aligning its body with the branch and 
^Published with the aid of a grant from the Museum of Comparative 
Zoology at Harvard College. 
Manuscript received by the editor September 9, 1969 
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