Postembryological Development of Spiderlings From Two PeruvianLatrodectus Populations

It is becoming increasingly clear that the solution of the complex taxonomic problems presented by the.black widow genus Latrodectus will require more basic biological data than are now available.Of particular importance in this regard is information on the postembryological development of color pattern.Many Latrodectus populations show marked interpopulation differences in color pattern particularly o the immature stages.It is difficult to assess the taxonomic sig- nificance of these differences without reliable information on the.de- velopment of these patterns in various populations.Little such information has been published.The.most extensive study was that done by Smithers (944) with Latrodectus mactans indistinctus.He raised spiderlings from three different areas in South Africa and recorded the.rate of development and the changes in color pattern after each molt.Unfortunately he confined his.ob- servations on color pattern to the emales.Recently we were able to obtain egg sacs from two different areas in Peru, Lima and Cuzco.We have reared 54 adults rom these, sacs and have recorded the 'changes in their color pattern after each molt.Morphologically these adults all appear to be Latrodectus mactans, probably the same as Latrodectus species "no. 3" of Abalos' cultures from Santiago del Estero Province in Argen-tina.The spiders were raised in the laboratory in St. Petersburg, using a technique previously described (McCrone and Levi, 964).A record was kept for each developing spider of the number of molts to maturity, the duration of the stadia, and the color pattern of each post-emergent instar.These data are presented in Tableand Figs.-9.The color patterns figured are the.basic patterns found in each population.There were slight individual differences in pattern; however, these, did not obscure the basic color patterns.From the illustrations it can be seen that some instars are more polymorphic than others (Fig. 2, 5, 6) even though the adults end up with more or less similar patterns in females (Fig. 9, 18, I9),