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FIGURE 7 in The water striders of Pakistan (Hemiptera: Heteroptera: Gerridae): new records from Punjab and first checklist for the country

FIGURE 7. Sampling site at Upper Jhelum canal near Pathan Colony, Kharian - Gujrat District (photo by R. Saleem).

FIGURE 6 in The water striders of Pakistan (Hemiptera: Heteroptera: Gerridae): new records from Punjab and first checklist for the country

FIGURE 6. Male genitalia of Naboandelus bergevini popovi Brown, 1951 from Lower Chenab canal (Gujranwala, Punjab, Pakistan): a–d) endosoma with sclerites in different positions; e) ventrite X, ventral view; f) ventrite X, dorsal view. Scale bar = 0.1 mm (photo by F. Cianferoni).

FIGURE 4 in The water striders of Pakistan (Hemiptera: Heteroptera: Gerridae): new records from Punjab and first checklist for the country

FIGURE 4. Habitus of Naboandelus bergevini popovi Brown, 1951 from Punjab (Pakistan): a) apterous male from Lower Chenab canal (Gujranwala) and b) apterous female from River Jhelum (Gujrat). Scale bar = 1 mm (photo by F. Cianferoni).

FIGURE 2 in The water striders of Pakistan (Hemiptera: Heteroptera: Gerridae): new records from Punjab and first checklist for the country

FIGURE 2. Specimens of Heterobates bilobatus (Esaki, 1927) from River Chenab, Head Marala (Sialkot, Punjab, Pakistan): a) apterous male (genital segment removed) and b) apterous female. Scale bar = 1 mm (photo by F. Cianferoni).

FIGURE 3 in The water striders of Pakistan (Hemiptera: Heteroptera: Gerridae): new records from Punjab and first checklist for the country

FIGURE 3. Male genitalia of Heterobates bilobatus (Esaki, 1927) from River Chenab, Head Marala (Sialkot, Punjab, Pakistan): a–d) endosoma with sclerites in different positions; e–h) parameres in different positions; i) proctiger. Scale bar = 0.1 mm (photo by F. Cianferoni).

FIGURE 1 in The water striders of Pakistan (Hemiptera: Heteroptera: Gerridae): new records from Punjab and first checklist for the country

FIGURE 1. Study area: a) Pakistan with Punjab Province highlighted; b) Punjab with the three districts forming the Industrial Triangle of Punjab highlighted; c) the Industrial Triangle of Punjab divided into the three districts of Gujrat, Gujranwala, and Sialkot, with the sampling sites indicated.

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Data from: Density-dependent sex-biased development of macroptery in a water strider

<p>In wing-polymorphic insects, wing morphs differ not only in dispersal capability but also in life history traits because of trade-offs between flight capability and reproduction. When the fitness benefits and costs of producing wings differ between males and females, sex-specific trade-offs can result in sex differences in the frequency of long-winged individuals. Furthermore, the social environment during development affects sex differences in wing development, but few empirical tests of this phenomenon have been performed to date. Here, I used the wing-dimorphic water strider <i>Tenagogerris euphrosyne</i> to test how rearing density and sex ratio affect the sex-specific development of long-winged dispersing morphs (i.e., sex-specific macroptery). I also used a full-sib, split-family breeding design to assess genetic effects on density-dependent, sex-specific macroptery. I reared water strider nymphs at either high or low densities and measured their wing development. I found that long-winged morphs developed more frequently in males than in females when individuals were reared in a high-density environment. However, the frequency of long-winged morphs was not biased according to sex when individuals were reared in a low-density environment. In addition, full-sib males and females showed similar macroptery incidence rates at low nymphal density, whereas the macroptery incidence rates differed between full-sib males and females at high nymphal density. Thus complex gene-by-environment-by-sex interactions may explain the density-specific levels of sex bias in macroptery, although this interpretation should be treated with some caution. Overall, my study provides empirical evidence for density-specific, sex-biased wing development. My findings suggest that social factors as well as abiotic factors can be important in determining sex-biased wing development in insects.</p>

FIG. 2 in Trolling for water striders: active searching for prey and the evolution of reduced webs in the spider Wendilgarda sp. (Araneae, Theridiosomatidae)

FIG. 2. Probable sequence of attachments by W. sp. near the water surface (schematic and not to scale). It was not clear from behavioural observations whether line a±b was doubled (as in drawing A) or broken and replaced (as it probably is in W. clara); nor was it certain whether point c was on the surface of the water or, more likely, just above it (see ®gure 7). It was con®rmed repeatedly, however, that the sticky line c±d (with balls in drawing C) was added to the non-sticky line rather than replacing it, as the sticky line was seen sagging brie¯y away from the straight vertical line. In two cases favourable lighting angles and background allowed con®rmation that line b±c was added to rather than replaced the line or lines laid just previously (a±b).

FIG. 7 in Trolling for water striders: active searching for prey and the evolution of reduced webs in the spider Wendilgarda sp. (Araneae, Theridiosomatidae)

FIG. 7. Microscopic views of silk on slides (stippled 5 puddles of sticky material; black masses 5 attachment discs, except for (E) where they 5 sticky material). (A) Lines of W. sp. ¯are away from central vertical line within masses of sticky material. (B) Attachment of W. sp. to water, showing attachment disc (presumed initiation of sticky silk) at bottom tip of vertical line. (C) Attachment of BCI creek W. sp. to water, showing attachment disc higher on vertical line and more sparse radial lines. (D) Attachment disc on a slack vertical line of W. sp. above section with sticky balls (e.g. d in ®gure 2), showing greater curliness of non-sticky lines. (E) Puddles of sticky material on a vertical line of W. sp., showing strong concentration of material at lower end of the line. Scale for (A), (C) and (D) at upper left.

FIG. 9 in Trolling for water striders: active searching for prey and the evolution of reduced webs in the spider Wendilgarda sp. (Araneae, Theridiosomatidae)

FIG. 9. Stages of the production of a second vertical line (A±D) and the initiation of a third line (E) by W. clara. The tight new vertical line (A, B) pulled the suspension line downward as the spider made the second descent; the tension then diminished and the angle in the suspension line became less acute (C; compare with B) as the spider extended the vertical line and then moved along the suspension line toward the previous vertical line (C). The spider apparently reeled up the suspension line as it then moved away from line 2 (D), because the white speck at the top of the new vertical line (dots in A±C) disappeared, and a white speck (presumably the accumulated reeled up silk) moved with the spider to the site where the next vertical line was laid (E). The positions of the white specks on the suspension line with respect to the vertical line in (A) ±(C) were not determined by direct observation; they are guesses based on the directions in which the specks moved and new lines were carried.

FIG. 5 in Trolling for water striders: active searching for prey and the evolution of reduced webs in the spider Wendilgarda sp. (Araneae, Theridiosomatidae)

FIG. 5. Probable mechanism used by spiders to jerk objects up out of the water (schematic). The spider ®rst reeled up the line, and thus tensed the entire line. When it then released this silk suddenly, the greater elasticity of the much longer line above the spider caused the spider to be displaced upward (arrow). The momentum of its body produced an upward jerk on the object when the line below its body became tight. This interpretation is tentative, because it was not possible to verify directly that the reeled up line was not broken (as in the drawing).

FIG. 8 in Trolling for water striders: active searching for prey and the evolution of reduced webs in the spider Wendilgarda sp. (Araneae, Theridiosomatidae)

FIG. 8. Tips of radial lines of an attachment of W. sp. to water, showing how they were progressively thinner near their tips (scale 5 0.05 mm).

FIG. 4 in Trolling for water striders: active searching for prey and the evolution of reduced webs in the spider Wendilgarda sp. (Araneae, Theridiosomatidae)

FIG. 4. Production of successive vertical sticky lines (schematic and not to scale). After moving slightly toward previous vertical lines and attaching the vertical line it had just laid (2) to the suspension line, the spider turned 180ss, attached its dragline to the broken end of the suspension line (small dot at the top of vertical line 2), and released silk, causing the two vertical lines to move away from it (arrow in (A); large dot gives a ®xed point of reference). Then it joined the broken ends of the suspension line (small dot at top of vertical line 3 in (B)), and descended to the water to make the next vertical line. Exact sites of broken ends of lines are estimated, as they were not observed directly.

FIG. 3 in Trolling for water striders: active searching for prey and the evolution of reduced webs in the spider Wendilgarda sp. (Araneae, Theridiosomatidae)

FIG. 3. Construction of three types of webs (schematic and not to scale; black balls represent sticky material). (A) The spider climbs to the suspension line after laying an additional short line to the water that was attached to the ®rst vertical line a few centimetres above the water's surface. (B) Spider moves a second vertical line (arrow) so its upper end will be close to or attached to that of the ®rst vertical line. Usually the upper portions of the two vertical lines then merged, resulting in a con®guration like that in (A). (C) Three vertical lines were attached to the suspension line and not subsequently moved.