266 
Psyche 
[June 
Since large differences in size may be accompanied by allometric 
differences it often becomes very difficult to decide whether a large 
and a small female belong to the same species. Also, the large and 
small specimens have differences in numbers of macrosetae. 
In addition, in the Araneidae there are often large differences in 
size between the sexes as the dwarfed males mature already after 
only a few molts, sometimes after fewer than half the number in 
females. Larger males, having undergone more molts, may resemble 
females more than they resemble smaller males (Gerhardt, 1929). 
Oddly, the smallest female and one of the larger males of A. 
illaudatus came out of the same egg-sac, hand-raised in P. Witt’s 
laboratory in North Carolina. This poses the question, to what 
extent the variable number of instars is environmentally determined? 
The egg-sac came from a building of the Southwestern Research 
Station near Portal, Arizona, where males are usually small and 
females large. 
According to older literature the minute size of many male orb- 
weavers prevents suitors from being mistaken for prey by the large 
female. This idea, which originated with Charles Darwin and Fried- 
rich Dahl (Gerhardt, 1929), is not convincing to me. In Gerhardt’s 
experiments neither large nor small males were attacked. It is much 
more likely that the differences in size, especially in warm climate 
spiders, is a secondary by-product of selection for different rates of 
ontogeny. A quick maturation of males, etc. is an adaptation against 
inbreeding. The tiny males mature after a few molts, perhaps months 
before sibling females undergo their 8 to 1 1 instars, and are forced 
to look for mature females from earlier broods or even from a 
different generation. [Witt (personal communication) reports that 
in his cultures of Araneus diadematus males mature long before 
females.] But then why do small males come in various sizes (as 
in A. illaudatus ), and why do hand-raised females vary in size? 
Is there genetic polymorphism for rate of development? 
Figs. 1-4. Left palpus, apical view. 1 . Araneus gemmoides Chamberlin 
and Ivie. 2. Araneus gemma (McCook). 3, 4. Araneus illaudatus (Gertsch 
and Mulaik). 3. (Portal, Arizona). 4. (hand-raised specimen, Portal, 
Arizona) . 
Figs. 5-11. Araneus ahigeatus new species. 5-8. Epigynum. 5. Ventral 
view, cleared. 6. Ventral view. 7. Posterior view, cleared. 8. Posterior 
view. 9-11. Left palpus. 9. Mesal. 10. Ventral. 11. Embolus in mesal view. 
Size indicators, 0.1 mm. 
