OP GENERATION. 323 



Lcpidoptera, for instance, in some of the Geometers (brumata, 

 namely, and many others), and in the genus Psyche, Latr. The 

 males of the Bombyccs and Geometers have doubly pectinated antennae, 

 whereas those of the female are much less strongly so, or merely simple 

 and setiform. The male Sphinges have longer narrower wings and 

 thinner bodies, the females have shorter broader wings and thicker 

 bodies. 



Among the Orthoptera, in Blatta also we detect a deficiency of wings 

 in the female, exclusive of which, in this order, the females are readily 

 distinguished by their projecting ovipositor, and many males have 

 differently formed wings, for example, the Locustce, in which, at the 

 base of the wing, there is a clear hyaline spot, which has been considered 

 as the vocal organ. 



The Dictyotoptera and Neuroptera exhibit in general no other differ- 

 ences but those derived from the sexual organs, in the Libellula*, only, 

 the males have stronger and larger anal fangs than the females ; besides 

 which, in the genus Agrion, the sexes differ considerably in colour, 

 the brighter colours are peculiar to the males, and the darker bronzy 

 ones to the females. In Boreus, Latr., a genus very nearly related to 

 Panorpa, to which the Panorpa hiemalis, Lin., (Gryllus proboscidcus, 

 Pz. Faun. Germ. XXII. 18.) belongs, the male has small hook- 

 shaped wings, but the female, which is furnished with an ovipositor, 

 is apterous. 



The sexual differences of the Diptera correspond in many instances 

 with those of the preceding orders. In the Cullces the males have 

 long, very hairy, plumose antennae, and sometimes, as in Culex and 

 Anopheles, very long, clavate palpi, of the same length as the proboscis. 

 Among the Tipulce the genera Erioptera and Ctenophora exhibit in 

 the male strongly pectinated ramose antennae, and much longer and 

 more delicate legs than the females. In Nematocera, Meig., (Hexa- 

 toma, Latr.) the male antennae are twice as long as the female. Among 

 the Syrphodea the larger approximate eyes form a distinct male cha- 

 racter ; and in some instances they have also, as in Xylota and Helo- 

 philus, thicker posterior femorae than the female, a character peculiar 

 also to some male Empis. Occasionally also, as in the genera Hilara 

 and Dolichopus, the males have distended tarsi upon either their 

 anterior or intermediate legs. 



The Hemiptera, lastly, exhibit striking and sometimes peculiar 

 sexual differences, among which the most remarkable is the vocal organ 



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