STY LOPS 



301 



difference really existing as to the method. When a Stylops 

 carried by an Insect (a Hymenopteron, be it noted, for we have 

 no information whatever as to Hemiptera) produces young, 

 they cover the body of the host as if it were powdered, being 

 excessively minute and their numbers very great ; many hundreds, 

 if not thousands, of young being produced by a single Stylops. 

 The species of the wasp genus Polistes are specially subject to 

 the attacks of Stylops ; they are social Insects, and a stylopised 

 specimen being sickly does not as a rule leave the nest ; in this 

 case the Stylops larva may therefore have but little difficulty in 

 finding its way to a Hymeuopterous larva, for even though it 

 may have to live for months before it has the chance of attaching 

 itself to a nest -building female, yet it is clearly in the right 

 neighbourhood. The bee genus Andrena has, however, quite 

 different habits ; normally a single female makes her nest under- 

 ground ; but in the case of a stylopised female it is certain that 

 no nest is built, and no larvae produced by a stylopised example, 

 so that the young triungulins must leave the body of the bee in 

 order to come near their prey. They can be active, and have 

 great powers of leaping, so that it is perhaps in this way possible 

 for them to attach themselves to a healthy female bee. 



We have still only very imperfect knowledge as to the struc- 

 ture and development of Strepsip- 

 tera. Indeed but little informa- 

 tion has been obtained since 

 1843. 1 Before that time the 

 mature female was supposed to be 

 a larva, and the triungulins found 

 in it to be parasites. Although 

 the erroneous character of these 

 views has been made clear, the 

 problems that have been sug- 

 gested present great difficulties. 

 Apparently the change from the 

 triungulin condition (Fig. 154) to 

 the parasitic larvae (Fig. 1 5 5, A, B) 

 is extremely great and abrupt, and it appears also that during 



1 Von Siebold, Arch. Naturges. ix. 1843, pp. 137-161. NassonofFs recent paper 

 is in Russian, but so far as \ve can gather (cf. Zool. Centralbl. i. 1894, p. 766), it does 

 not add greatly to the data furnished by von Siebold. 



FIG. 155. Portion of early stages of 

 Xenos rossii. (After von Siebold.) 

 A, Small male larva ; B, small female 

 larva ; C, full-growu male larva ; D, 

 full-grown female larva ; E, the so- 

 called " cephalothorax " and adjacent 

 segment of adult female. (The newly- 

 hatched larva is very much like that 

 of Stylops shown in Fig. 154.) 



