The Hog Louse 651 



Time of development from first-stage larva to mature 



adult 16 to 18 days 



Temperature and other conditions 35° C, continually 



next to body, in 

 vials 



Number of feedings in 24 hours 1 to 4 



Duration of cycle from egg to egg 29 to 33 days 



THE EARLY STAGES 



The newly hatched louse has 5-segmented antennae and a 9-segmented 

 abdomen, as are found in the adult. The claws and the pad, already 

 described, are present as in the adult, but no joint between the tibia and the 

 tarsus appears until after the final molt (Plate LVIII, 1 and 5). Attention ' 

 was drawn to this point by Gillette in his brief description of the species 

 written for Coburn (1912:497). The head is large in proportion to the 

 almost colorless body. Only the claws, and the sides of the head in the 

 region of the clypcus, show marked chitinization. During the first instar 

 (Plate LVIII, 3) the dark color gradually extends along the lateral and pos- 

 terior dorsal regions of the head and the thorax, the legs become more 

 strongly chitinized, and there is some indication of the transverse abdominal 

 plates. The chitinous plates of the pleurites are represented by small, Kght 

 brown spots close to the spiracles. In the second instar (Plate LVIII, 4) 

 the chitinization is generally more marked, but the buccal tube can still 

 be clearly seen through the integument. The transverse abdominal plates 

 are more developed, the plates of the pleurites are approximately four times 

 as large as in the first instar, and between these two arc small circular 

 chitinous areas. In the third instar (Plate LVIII, 5) the head is more 

 strongly chitinized and the buccal tube can no longer be seen throughout 

 its length. The plates of the pleurites resemljle those of the adult but 

 are somewhat lighter in colour. The ninth abdominal segment shows 

 no chitinization but is turned slightly dorsad, and the first antennal 

 segment, which in the previous stages was almost of the same diameter 

 as the four other segments, is now considerably larger than these. At 

 the third molt the chitinous plates, which are the external indications of 

 sex, appear at the posterior end of the body. In both male and female, 

 maturity is indicated by a sternal chitinous plate which appears on the 

 thorax about the third day after the final molt (Plate LVIII, 6). The 



