February, '13J QUAYLE: RED spider enemies 87 



Scolothrips sexmaculatus Pergande. Our data on carnivorous thrips 

 are fragamentry except for the species named which has been observed 

 to feed on spiders and mites. This species has been repeatedly observed 

 to feed on the citrus red spider and occurs most abundantly during 

 the winter and early spring. Generally the eggs and younger spiders 

 are eaten, but occasionally fully mature spiders are attacked. The 

 time required to consume the contents of eggs and spiders varied from 

 three to seven or eight minutes. Most of the contents of the egg were 

 taken from a single puncture, then two or three additional punctures 

 would be made on different sides and lower down, to get what little of 

 the contents remained. In the case of the spiders themselves, after 

 taking most of the body contents, the spider would be rolled around 

 and punctured from different sides, the revolving being done by the 

 fore legs of the thrips. The spiders were attacked mostly before the 

 first or second molt and usually at a time when the spider was in a 

 quiescent stage just preliminary to the molting process. All stages 

 of the thrips, barring the pupa, have been noted to feed on the spiders. 



Stethorus picip^s Csy. This is the commonest species of the Coccin- 

 ellidse that was found to feed on the red spider, in fact, the only one 

 of any consequence. 



Feeding records on the larva of this beetle showed that in the case 

 of one that lived 20 days it consumed a total of 189 spiders or an average 

 of 6 or 7 per day. Another devoured a total of 110 spiders in 13 days 

 of 8+ per day. 



Arthrocnodax occidentalis Felt. This is a species of Itonididse, the 

 larva of which has been found to feed on the red spider. It has been 

 observed to feed on Tetranychus mytilaspidis, T. himaculatus and T. 

 sexmaculatus, being most abundant on the last species, probably be- 

 cause they hve in definite colonies and food is obtained with less moving 

 ab6ut. Where the number of these Dipterous larvse is large their effect 

 on' checking the spider is considerable. One on which records were 

 kept consumed 165 spiders during a period of 15 days, or 11 per day, 

 and another had 380 spiders to its credit in a period of 17 days or 12 

 per day. This species was sent to Doctor Felt for identification, who 

 stated that it was a new* species and it has since been described in a 

 recent number of the Journal of this Association. 



Of the other better known enemies of spiders I will mention briefly 

 but one, one of the Brown lace wings, Hemerohius californicus which 

 is very voracious and eats a large number of spiders during its develop- 

 ment. Records show that one of these larvae ate 532 spiders in 17 

 days, 31 per day and another a total of 897 spiders in 20 days or an 

 average of 44 per day when it died, from overeating or otherwise, 

 though this one was no doubt mature and ready for pupation. 



