382 William Morton Wheeler 



male, for the latter must have to insert its penis along the ventral 

 surface of the head of the female and immediately under the over- 

 lapping sternite or tergite of the host. 



That several of the conclusions drawn from the table on page 

 379 cannot have general validity is shown by comparing them with 

 the statistics of other observers. Home ('72) says that the speci- 

 mens of Polistes hebraeus which he observed in India were "ex- 

 tremely troubled with Stylops (Xenos), every fifth or sixth one 

 taken having a female of one under one of the segments of the abdo- 

 men." Theobald ('92) found that among 180 Andrena lapponica 

 taken in England during 1887, 105 or 58 percent contained Stylops; 

 of 60 bees of the same species, taken in 1888, 54 or 90 per cent were 

 badly stylopized. He believes that the female Andrenae are more 

 afflicted with the parasites than the males, and he records the num- 

 ber of Stylops found in the 54 bees taken during 1888 as comprising 

 33 females and 21 males; 2 females each contained 2, 3 males con- 

 tained 2, 25 females and 18 males i each. The corresponding 

 numbers for 40 stylopized specimens of Andrena nigroasnea 

 were 3 females each with 3 Stylops, i male with 3, 3 females 

 with 2, 5 males with 2, 16 females with i and 12 males with I, 

 making 22 females and 18 males. On the basis of these figures 

 Theobald differs from Perkins ('92), who found the males of 

 various Andrenae and Halicti more frequently stylopized than 

 the females. This author says that he has seen hundreds of 

 stylopized male Halictus tumulorum, but has never seen a female 

 in this condition. Although Theobald's conclusions agree with 

 my own, his data do not furnish very strong support in favor of 

 his contention, since in A. lapponica the ratio of parasitized males 

 to females is i : 1.5 and in A. nigroaenea onl^ i : 1.2. Skinner ('03) 

 counted 34 stylopized individuals among 140 Polistes texanus, 

 which he found at Pecos, Texas. He says that " most of theXenos 

 appeared to be females and only 4 males were secured." 



The percentage in this case is very similar to that which I found 

 in P. metricus. Brues ('05) has published some statistics on two 

 colonies of the Texan P. annularis infested with Xenos nigrescens 

 Brues and X. pallidus Brues. In these cases the amount of para. 



