1972] 
Cooper — Boreus 
279 
However, I find that the genotypic species of Euboreus, namely 
B. nivoriunduf, has XO (male) — XX (female) sex determination 
and genitalia that are extremely similar to those of B. hyemalis * } 
thus the testes are single lobed and have fused calyces (fig. 10), and 
there is an extremely elongated spermathecal duct in the female 
(fig. 11) that is “coiled like a watch spring”, just as Potter (1938) 
described it for B. hyemalis. Interestingly, XO-XX male hetero- 
gamety is the general mode of sex determination for the Mecoptera 
so far studied ( Panorpa Ullerich 1961; Bittacus, Matthey 1950; 
Chorista , Bush 1967; and Merope, Cooper, unpublished ) 3 , and is 
most probably primitive; primitive also is the very elongated sperma- 
thecal duct, a condition which Potter (1938) places among the five 
“most striking of the typically Mecopterous characters of the order”. 
There are, therefore, no grounds at present for viewing Lestage’s 
Euboreus as a useful taxonomic set, or even for attributing to its 
members as a group the emphasis which Lestage gave them as more 
primitive forms. Quite to the contrary, “E” notoperates indeed 
seems to be the least primitive among all the Boreus known. Its 
“advanced” characters include the long hypostomal bridge, loss of 
the median ocellus and the corporatentorial bridge 4 , loss of the brush 
of fine pubescence on the hind wing, the unparalleled reduction of 
the submedian tooth-complex of the dististyles, the peculiar apicolat- 
eral blades of the 10th tergum of the female, and the distinctive 
spermatheca with its very short duct — all exceptional departures 
from the usual conditions in the Boreidae. Except for the marked 
reduction of the submedian complex of the dististyles, B. brevicaudus 
shares all of the external peculiarities with B. notoperates , and quite 
likely it possesses most or all of the remaining anatomical departures 
as well. These two Boreus , then, are the most specialized boreids 
known. Conversely, members of Lestage’s “Boreus” have a quite 
generalized morphology, and should the tergal apophyses of their 
males prove to be vestiges of notal appendages homologous to those 
of Notiothaumids, Panorpids, and Panorpodids (Crampton 1931; 
Mickoleit 1971a), they are evidently the most “primitive” forms 
known (but see ftnt. 2). At best they comprise a species-group 
within Boreus as now defined, namely the hyemalis-group. 
3 Also see Atchley and Jackson (1970). 
4 Boreus nivoriundus (Otanes 1922), B. hyemalis (Slais 1947), B. uni- 
color and B. calif ornicus (Hepburn 1969), and as I have found for B, 
hrumalis, have 3 ocelli and a divided occipital foramen. At present the 
Boreidae is the only family of Mecoptera within which the number of 
ocelli varies, and in which the occipital foramen occurs in both states: 
divided and undivided (see Hepburn’s fine study). 
