Water bugs, like other aquatic insects, should bo 

 transported alive in containers with moist water 

 plants rather than in jars of sloshing water. They 

 do well in home aquaria if .cared for daily. However, 

 the mortality is usually quite high during successive 

 molts, and very few species have been reared through 



• many generations. For the true aquatics a constant 

 supply of fresh air is desirable and can be had by 

 bubbling through a line from an aquarium aerator. 

 Shore bugs do well in small jars containing a sub- 

 strate of plaster of Paris darkened with lamp black. 

 Excessive moisture must be avoided, lest the small 

 nymphs become entangled in the surface film. 



Food can be provided by sweeping terrestrial vege- 



I tation, by maintaining a culture bottle of Drosophila, 

 by supplying freshly killed or immobilized house 

 flies, or by keeping a culture of mosquito larvae or 

 brine shrimp. 



Bugs must be kept in individual containers to avoid 

 cannibalism and to keep track of cast skins. 



SYSTEMATICA 



Characters. — Figure 7:3 shows the external struc- 

 tures of a corixid. Other bugs vary in details but 

 these drawings will suffice for a general understand- 

 ing of the group. It should be noted that the first 

 visible abdominal segment as seen from below is 

 really the second segment. The genital capsule or 

 pygophore is usually concealed and is in the ninth 

 segment. Genitalia are used for the separation of 

 species in most groups of aquatic Hemiptera. The 

 genital segment may be removed in dried specimens 

 by softening the tip of the abdomen in a solution of 

 phenol (1/3), water (1/3), and alcohol (1/3). A dis- 

 secting needle with its tip bent should be inserted 

 at the side of the eighth segment and then twisted 

 and drawn out, pulling die genital segment. For 

 specimens preserved in alcohol the operation is 

 simpler, because the parts are soft enough to dissect 

 without special relaxing fluid. Genitalia, including 

 the claspers and aedeagus, are best studied in fluid, 

 but in a few cases the structures are hard enough to 

 observe in a dried condition. The latter can be glued 

 to a card beneath the specimen, but the genitalia of 

 most water bugs should be mounted in balsam on 

 microscope slides or between cover slips on small 

 cards or points beneath the specimen. Perhaps the 

 commonest method of preserving genitalia is in micro 

 vials containing glycerine. These are stoppered with 

 long cylindrical corks and are held at an angle on 

 the pin below the insect, care being taken to keep 

 the glycerine from permanent contact with the cork. 



Measurements are made with an eye-piece microm- 

 eter. Total length is the over-all length of the 

 insect in one plane. Antennal segments are measured 

 ignoring the small, intercalary, ringlike segments 

 seen in some forms. 



187 

 Usinger: Hemiptera 



Key to the Families of Aquatic and Semlaquatlc Hemiptera 

 Adults and Nymphs. 



1. Antennae shorter than head, inserted beneath ey , not 

 visible from above (fig. 7:3a, b) except in OcMi-ridae 

 (fig. 7:23). True aquatics and a few shore buns. B< I 

 Cryptocerata 2 



— Antennae longer than head, inserted in front of eyes 

 and plainly visible from above (fig. 7:24). Shore bugs 

 and surface bugs. Series Gymnocerata 9 



2. Rostrum very short, broad, scarcely distinguishable 

 from the broad apex of head, not distinctly segmented 

 (fig. 7:36); front tarsi developed as comblike palae 

 (fig. 7:9); base of head overlapping front margin of 

 pronotum (fig. 7:6); nymphs with 3 dorsal abdominal 

 scent gland openings COlilXIDAE 



— Rostrum cylindrical or cone-shaped and distinctly 3- or 

 4-segmented; front tarsi not developed as comblike 

 palae; base of head inserted in pronotum; nymphs with 

 scent gland openings lacking or present on only one 

 segment 3 



3. Abdomen with a pair of long, slender posterior append- 

 ages, forming a respiratory siphon; hind coxae short, 

 free, rotary NEPIDAE 



— Abdomen without a pair of long, slender posterior 

 appendages; hind coxae broadly joined to thoracic 

 pleura 4 



4. Ocelli absent; middle and hind legs provided with more 

 or less extensive fringes of long swimming hairs. 

 Water bugs 5 



— Ocelli present; middle and hind legs without fringes of 

 swimming hairs. Shore bugs 8 



5. Front legs not chelate; body strongly convex above 



6 



— Front legs chelate, the femora enlarged and tibiae 

 curved and articulating against femora; body sub- 

 flattened above 7 



6. Form elongate; adults large, more than 5 mm.; hind 

 legs long, oarlike, without distinct claws (fig. 7:10) 

 NOTONECTEDAE 



— Form oval, adults small, less than 3 mm.; hind legs not 

 long and oarlike, with 2 distinct claws PLEIDAE 



7. Membrane of hemelytra with reticulate veins, abdomen 

 with a pair of short, flat, retractile posterior appendages 

 (fig. 7:16); nymphs without dorsal abdominal scent gland 

 openings BELOSTOMATIDAE 



— Membrane of hemelytra without veins; abdomen without 

 posterior, straplike appendages (fig. 7:13); nymphs with 

 a pair of widely separated scent gland openings between 

 2nd and 3rd abdominal tergites (fig. 7:12) 



NAUCORIDAE 



8. Front legs raptorial, the femora very broad and grooved 

 along inner edges nearest the curved tibiae; antennae 

 concealed in grooves beneath strongly protuberant eyes 

 (fig. 7:21) GELASTOCORIDAE 



— Front legs similar to middle pair, fitted for running; 

 antennae exposed (fig. 7:23) OCHTERIDAE 



9. Hind coxae short, freely movable, rotatory. Shore and 

 surface bugs 10 



— Hind coxae long, broadly joined to thoracic pleura. 

 Shore bugs 15 



10. Claws of at least front tarsi inserted before apex ... 11 



— Claws all inserted at tips of tarsi 12 



11. Hind femora very long, greatly exceeding apex of 

 abdomen (fig. 7:24); adults with a median metasternal 

 scent gland opening GERRIDAE 



— Hind femora scarcely, if at all, surpassing tip of 

 abdomen (fig. 7:29); adults with lateral metathoracic 

 scent gland openings VELHDAE 



12. Head as long as the entire thorax; body long and 

 cylindrical (fig. 7:32); nymphs without dorsal abdominal 

 scent gland openings HYDROMETRIDAE 



