THE TAXONOMIC PROBLEM OF SEXUAL 
DIMORPHISM IN SPIDERS AND A SYNONYMY IN 
MYRMECO TYPUS (ARANEAE, CLUBIONIDAE)' 1 
By Jonathan Reiskind 
Biological Laboratories, Harvard University 
With the major exception of many of the vertebrate groups, some 
mollusks, and butterflies, much of the current evolutionary work in 
zoology requires, concurrently, research at the “alpha” level of tax- 
onomy in which species are characterized and named (Mayr, Linsley 
and Usinger, 1953). While this appears to be just a continuation of 
the work of Linnaeus, Clerck, and others it is by no means an old- 
fashioned, unchanging endeavor. With the advent of Darwin’s theory 
and, later, the new systematics of the 20th century alpha tax- 
onomy has continued to incorporate the most recent advances in 
evolutionary biology. Behavioral, ecological, distributional, physiologi- 
cal and biochemical characteristics must be utilized in this “lowest 
level” of taxonomy in addition to the traditional morphology. I11 
this way the typological and morphological result of overlooking two 
sibling species or splitting a single species into two species can be 
avoided. An error of the latter type is often a result of sexual dimor- 
phism. 
In non-hermaphroditic, sexually reproducing organisms there 
usually exists some sort of morphological sexual dimorphism. Some- 
times this is limited to the sexual structures themselves, but more 
often it is extended to secondary sexual characters. In spiders there 
are three types of secondary characters. Type one is intimately in- 
volved in the physical act of copulation and is represented by the 
pedipalps of males which are modified into organs for the transfer- 
ence of seminal fluid to the female during mating. Type two is as- 
sociated with the courtship before mating which includes the bizarre 
and colorful structures that are observed in the Salticidae (especially 
the males) as well as the size differences in certain argiopoid groups. 
All structures resulting from sexual selection or reproductive re- 
quirements fall into this second type. Type three is unrelated to the 
procreative process and includes size, color and shape differences 
whose origins are either due to non-sexual selection or possible pleio- 
tropic effects. 
’Research a by-product of National Institutes of Health Grant No. AI-01944 
to Dr. H. W. Levi, and of an NSF Graduate Fellowship. 
Manuscript received by the editor January 28, 1966. 
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