ANATOMY AND PHYSIOLOGY 



Blind Insects. Many larvae, surrounded by an abundance of food 

 and living often in darkness, need no eyes and have none ; this is true of 

 the dipterous "maggots" and many other sedentary larvae, particularly 

 such as are internal parasites (Tachinidae, Ichneumonidae) , or such as 

 feed within the tissues of plants (many Buprestidae, Cerambycidae and 

 Curculionidae). Subterranean or cavernicolous insects are either-eyeless 

 or else their eyes are more or less degenerate, according to the amount of 

 light to which they have access. The statement is made that blind in- 

 sects ,never have functional wings. 



Antennae. The antennae, never more than a single pair (though 

 embryonic " second antennae" occur in Thysanura and Collembola), are 

 situated near the compound eyes and frequently between them. With 

 rare exceptions the antennae have always several and usually many seg- 

 ments. In form these organs are exceedingly varied, tliough many of 

 them may be referred to the types represented in Figs. 41-43. 



Though homologous in all insects, the antennae are by no means equiv- 

 alent in function. They are commonly tactile (grasshoppers, etc.) or 

 olfactory (beetles, moths) and occasionally auditory (mosquito), as 

 described beyond, but may be adapted for other than sensory functions. 

 Thus the antennae of the aquatic beetle Hydrophilus are used in connection 

 with respiration and those of the male 

 Meloe to hold the female. 



Sexual Differences in Anten- 

 nas. In moths of the family Saturnii- 

 dae (S. cecropia, C. promethea, etc.) the 

 pectinate antennae of the male are 

 larger and more feathered than those 

 of the female, and differ also in having 

 more segments (Fig. 42). Here the 

 antennae are chiefly olfactory, and the 

 reason for their greater development in 

 the male appears from the fact that the 

 male seeks out the female by means of 

 the sense of smell and depends upon 

 his antennae to perceive the odor ema- 

 nating from the opposite sex. 



The plumose antennae of the male mosquito (Fig. 43) are highly de- 

 veloped organs of hearing, and are used to locate the female; they have 

 delicate fibrillae of various lengths, some of which are thrown into sym- 

 pathetic vibration by the note of the female (p. 85). 



FIG. 42. Antennae of a moth, Samia 

 cecropia. A, male; B, female. 



