SEXUAL BIOLOGY, CHROMOSOMES, DEVELOPMENT, 
LIFE HISTORIES AND PARASITES OF BOREUS, 
ESPECIALLY OF B. NOTOPERATES. 
A SOUTHERN CALIFORNIA BOREUS. 
II. (MECOPTERA: BOREIDAE)* 
By Kenneth W. Cooper 
University of California, Riverside 
California 92502 
Introduction 
This, the second of three accounts devoted primarily to Boreus 
notoperates Cooper, deals with aspects of its life history. The sub- 
jects include, among others, sex ratio, mating, developmental stages, 
a brief comparative account of its cytology, its host mosses and pecul- 
iar adaptation to a life in their thin sods on diorite boulders in a 
region annually subject to long periods of drought and considerable 
heat. All of this is placed in a framework of what is now known 
for the other species of Boreus on these topics. 
Though some fifty or so articles are referred to or discussed that 
are devoted to, or comment upon, Boreus , there are an additional 
sixty to seventy more papers and accounts which, though all have 
been consulted, either do not bear directly on the topics treated, or 
seem wholly derivative. My choice of references is based upon their 
substantial treatment of a subject, their content of new observations 
or ideas, or the need to correct a standing error. To these sources, 
I have added my own unpublished observations on B. brumalis Fitch 
and B. nivoriundus Fitch where relevant. The overall aim, then, is 
to draw together, to compare, and, where possible, to generalize 
what is known of the species of Boreus on the topics presented and 
on which I have information derived from B. notoperates. 
Among the matters given emphasis are: the likelihood that species 
of Boreus have a sex ratio approaching equality (a debated topic) ; 
the fact that B. notoperates is the only species (of eight for which 
information is known) that deviates in its mating; the curious re- 
ciprocal intromission at mating by male and female alike, and the 
anatomical relations of their parts; the conservative nature of the 
chromosomal cytology of Boreus and other scorpion flies as compared 
with Panorpa; the prevalence of a larval epistomal suture, which 
* Manuscript received by the editor February 10, 1974. 
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