240 PROCEEDINGS OF THE NATIONAL MUSEUM vol. in 



from two to five weeks, depending upon external conditions of which 

 humidity and temperature are the most important factors. 



Egg: Dull brown to black, somewhat pear-shaped, finely reticu- 

 lated, and quite small, rarely exceeding 0.35 mm. in length. Millot 

 (1938) referred to an adhesive disc on the posterior end of the egg of 

 pallipes Latreille which was used for its attachment. However, in 

 adaptatus, new species, the disc is apparently wanting, and the eggs 

 when laid seem to be sticky over the entire surface so as to adhere to 

 the substrate at nearly any angle. 



FiRST-iNSTAR LARVA : The planidial larvae upon emergence may be 

 seen "standing" erect beside the egg, and are ready in this position to 

 attach themselves to any host which may pass by. There may be 

 several days of this "standing" or "walking," the latter being done 

 by bending the head down to the sm'face and moving the caudal 

 segment forward in a fashion similar to that of a measuring-worm. 

 If the larva does not come in contact with a suitable host, it may drop 

 from the substrate to the ground or jump from place to place by 

 springing itself into the air. I have observed that, upon contact 

 with a host spider, the larva appears to be careful not to disturb it 

 and moves only when the spider itself moves. At times a spider has 

 been observed to remain quiet for hours, and during this period the 

 Ogcodes larva has done likewise. 



In most cases that I have seen, the larvae seemed to prefer entering 

 the host along the dorsal-median-anterior region of the abdomen; 

 and the total length of time involved to complete the parasite entrance 

 was from 1 to 24 hours for adaptatus, new species. Several larvae were 

 observed to enter the host through the intersegmental membranes of 

 the legs, but about 50 percent of the larvae moved over the host's body 

 and entered the abdomen as above, even when their primary attach- 

 ment to the host was some distance from the abdomen. In my experi- 

 ments active larvae of adaptatus, new species, have lived up to 10 days, 

 but the average longevity was only 6 days. For other information on 

 larval habits see Clausen (1940). 



The first-instar larva (pi. 2, figs. 4, 5), which is best termed a 

 planidium, is composed of 12 segments (the head and 11 somites), 

 each weU-sclerotized, and, except for the head segment, bearing various 

 numbers and lengths of strong or weak setae. The larva measures 

 about 0.30 mm. in length, and about 0.05 mm. in width. The head 

 is minute and consists of a pair of anterior oral hooks, a pair of small 

 dorsal setae, and a pair of apparently two-segmented, ventral an- 

 tennae, each with a short distal seta. The mouth is just anterior to 

 the point of antennal insertion. The buccopharyngeal armature 

 consists either of two dorsolateral rods and one medioventral rod or 

 two dorsolateral and two ventrolateral rods that extend back from the 



