io6 
Psyche 
[June 
mechanism for controlling the final molt. Suppose that constant 
conditions of warmth and abundance of food produce a regular in- 
terval of four weeks between molts throughout the summer but that 
a hormone is activated following the penultimate instar which in- 
hibits further molting. Gradually, this inhibitory substance wears 
off. Then the spider can respond to environmental conditions again 
and if, during a brief sampling period, it is exposed to favorable 
environmental conditions, it will molt. Such a mechanism could be 
highly adaptive as the spiders would not initiate a disastrous breeding 
season during an Indian Summer, and could take advantage of an 
early spring. 
Some fragmentary evidence supports this hypothesis: occasionally, 
spiders have been collected in their heavy webs during the winter, 
and brought to the laboratory where they soon resumed feeding. 
Under these conditions, two penultimate males collected on 4 Decem- 
ber became mature on 5 January and 12 January respectively. Further 
experiments along these lines, that is, with favorable environmental 
conditions administered in short samples at different times during the 
winter would test the suggestions on inhibition. Furthermore, the 
favorable conditions should be specified more closely, as Turnbull 
(1962, 1965) has done for the relationship between daily food con- 
sumption and development in Linyphia triangularis and A gelenopsis 
potteri. 
References 
Gardner, B. T. 
1965. Observations on three species of Phidippus jumping spiders 
(Araneae: Salticidae). Psyche, 72: 133-147. 
Turnbull, A. L. 
1962. Quantitative studies of the food of Linyphia triangularis Clerck 
(Araneae: Linyphiidae) . Can. Ent., 94: 1233-1249. 
1965. Effects of Prey Abundance on the Development of the Spider 
Agelenopsis potteri (Blackwall) (Araneae: Agelenidae). Can. 
Ent., 97: 141-147. 
