78 THE EEPORT OF THE No. 36 



reminds one of that of the Hammer-headed Shark; and the eyes project from the 

 sides of it. These dragon-flies, like others of the Odonata, can turn their heads half 

 round on the neck, and so look over their shoulders. 



Another insect with large and protruding eyes is the Giant Water Bug, Bel- 

 ostoma Americana (Fig. 14). So far do the eyes of this insect protrude one might 

 almost expect that, in the wild dashes of the insect through the upper air, and 

 into and under the water, they would be swept from their position. But a remark- 

 able provision prevents the danger; from the centre of the saucer-like eye-socket 

 arises a stput support, flattened out a little at the top — somewhat spool-shaped — 

 and around this the eyelets of the compound eye are compressed. (Fig. 15). 



In the Diving Beetle, Dytiscus Harrisii (Fig. 15), an insect of very similar 

 habits to B. Americana, the eye is so placed in the side of the head that the creature 

 can see both above and below; and the organ is protected by a curved extension of 

 the pro-thoracic shield. 



The like protection is afforded to the eye in water-beetles of other genera — 

 Hydrocharis, Colymbetes, Acilius, etc., while in Dineutes the eye appears to pass 

 through the substance of the head, so that the insect seems to have four eyes — two 

 above and two below. 



That widely different and very minute insect the White Fly of the greenhouse 

 appears to have eyes similarly arranged to those of Dineutes. In the fly the eyes 

 appear as two black dots above, and two black dots beneath the head. 



The mouth organs of insects vary considerably to suit their different habits. 

 There is a striking difference in the mandibles of the male and female imagos of 

 the Giant Water Fly, Corydalis cornutus (Fig. 16). This is the more remarkable 

 because in the larval and pupal stages of the sexes the organs apparently are alike. 

 Some years ago I traced the life-history of this species through its metamorphoses. 

 I saw the nymph draw itself about in its cyst, by means of its formidable mandibles; 

 and I expected that, when the change to the imago came, the insect would prove to 

 be a female; but lo, when it came, and tlie imago burst from the nymphal case, 

 the mandibles were extended (I presume by inflation) into the preposterous organs 

 we see in the male. Why is this difference between the male and the female 

 mandibles ? It is that the male may be able to give a loving embrace to the well- 

 defended neck of its mate. 



How strangely the lips and jaws of the dragon-fly work, in masticating its 

 food, as if they were at cross purposes, the lips perpendicularly, the jaws horizon- 

 tally — they are two pairs of very effective cutting knives. 



Belostoma Americana lives by sucking the life-fluids of its prey, and is fur- 

 nished with a stout beak-like proboscis, about a quarter of an inch long. This pro- 

 boscis consists of an outer pointed case, having a longitudinal slit in front, and 

 of an awl-shaped sucking instrument enclosed in a divided sheath barbed at the 

 extremity. It is a formidable weapon. 



The bug clings, by means of its powerful front legs, which are terminated 

 with sharp claws, to the fish or other creature that it assails, and thrusts its pro- 

 boscis into its victim. 



The Eeduviidse, or " Assassin Bugs," are furnished with beaks of like con- 

 struction. The stories told us of the "Kissing Bug" have led us to understand 

 how dangerous, under some circumstances, these weapons may become. 



The proboscis of the House Fly is terminated by two ridged valves with which 

 the insect scrapes up its food. Those who have volumes bound in sheep-skin, 

 and exposed in open cases, will soon find, from the roughness and loss of gloss in 

 the binding, that the flies have been at work upon the dressing of the leather. 



