It is a matter of great difficulty to procure material for the prosecution of this study; the fact that the instars to be observed exist only in the interior of a few Hymenopterous larvae, which in the case of the bee, _Andrena_, are concealed under ground; and in the case of the wasps, _Polistes_, placed in cells in a nest of wasps, adds greatly to the difficulty. It is therefore of interest to know that Strepsiptera occur in Insects with incomplete {303}metamorphosis. They have been observed in several species of Homoptera; and the writer has a large Pentatomid bug of the genus _Callidea_, which bears a female Strepsipteron apparently of large size. This bug[163] is abundant and widely distributed in Eastern Asia, and it may prove comparatively easy to keep stylopised examples under observation. Both v. Siebold and Nassonoff think parthenogenesis occurs in Strepsiptera, but there appear to be no facts to warrant this supposition. Von Siebold speaks of the phenomena of Strepsipterous reproduction as paedogenesis, or pseudo-paedogenesis, but we must agree with Meinert that they cannot be so classed. The males of Strepsiptera live for only a very short time, and are very difficult of observation. According to Hubbard the males of _Xenos_ dash about so rapidly that the eye cannot see them, and they create great agitation amongst the wasps in the colonies of which they are bred. Apparently they are produced in great numbers, and their life consists of only fifteen or twenty minutes of fiery energy. The males of _Stylops_ are not exposed to such dangers as those of _Xenos_, and apparently live somewhat longer—a day or two, and even three days are on record. The individuals of _Andrena_ parasitised by _Stylops_ are apparently greatly affected in their economy and appear earlier in the season than other individuals; this perhaps may be a reason, coupled with their short lives, for their being comparatively rarely met with by entomologists. [Illustration: Fig. 156.—Abdomen of a wasp (_Polistes hebraeus_) with a Strepsipteron (_Xenos_ ♀) in position, one of the dorsal plates of the wasp's abdomen being removed. _a_, Projection of part of the parasite; _b_, line indicating the position of the removed dorsal plate.] It is not possible at present to form a valid opinion as to whether Stylopidae are a division of Coleoptera or a separate Order. Von Siebold considered them a distinct Order, and Nassonoff, who has recently discussed the question, is also of that opinion. {304}CHAPTER VI LEPIDOPTERA—OR BUTTERFLIES AND MOTHS ORDER VI. LEPIDOPTERA.