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Invertebrates

Mossy Rose Gall Wasp Larvae Cease Feeding

10-31-14 mossy rose gall IMG_0404In the spring, the 4mm-long cynipid gall wasp, Diplolepis rosae, lays up to 60 eggs (through parthenogenesis) inside the leaf bud of a rose bush. A week later, the eggs hatch and the larvae begin feeding on the leaf bud. This stimulates the abnormal growth of plant tissue, and a Mossy Rose Gall, covered with a dense mass of sticky branched filaments, is formed. The gall provides the larvae with food and shelter through the summer. In late October, when the Mossy Rose Gall is at its most colorful, the larvae stop eating and pass into the prepupal stage, in which they overwinter inside the gall. In February or March, the prepupae undergo a final molt and become pupae. If the pupae aren’t extracted and eaten by a bird during the winter or parasitized by another insect, adult wasps exit the gall in the spring and begin the cycle all over again.

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Predaceous Diving Beetles Remaining Active

10-9-14   p. diving beetle 143While meadows and fields are experiencing a sharp decline in insect life at this time of year, one habitat where insects remain active in the fall and often through the winter is ponds. Among the year-round active pond invertebrates are Predaceous Diving Beetles, which can still be observed as they row through the water, intermittently surfacing to thrust their abdomen above the water line in order to procure a bubble of air from which they breathe. Their middle and hind legs are fringed with long hairs, making them efficient at rowing through the water in search of prey or detritus to eat.

Predaceous Diving Beetles lay their eggs on and in plants above the waterline in early spring. When the eggs hatch, the larvae drop into the water. Mature larvae crawl out of the water to pupate in damp chambers on the shoreline. They emerge as adults and re-enter the water, where they remain active through the winter, under the ice. (Water Scavenger Beetles look a lot like Predaceous Diving Beetles, but they stroke first with one leg, then another, not simultaneously like Predaceous Diving Beetles, and they come to the surface of water head first to secure air.)

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Black Vine Weevil Larvae Crawling Deep Underground

black vine weevil 150Black vine weevil larvae overwinter in the soil. In the spring, the flightless adults emerge and feed at night on the outer edges of leaves, causing the leaves to have a notched margin. They mate and lay as many as 500 eggs in the soil near the base of host plants. The larvae hatch in a week or two and feed on plant roots until cold temperatures drive them further underground. The larval stage is quite destructive, especially to landscape plants such as rhododendron and azalea. Female black vine weevils have the ability to reproduce parthenogenetically. Fertilization of eggs is required to produce males, but no males have been observed in North America. (photo: adult black vine weevil on Jack-in-the-Pulpit fruit)

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Funnel Weaving Spiders Spinning Last Webs of the Year

10-16-14 funnel weaver web 045A number of unrelated spider families in North America spin webs with funnel-shaped retreats. These spiders are all referred to as funnel weavers. The spider lies in wait in the funnel, and when an insect flies into or lands on the web, the spider rushes out, checks to see if it is prey, and if it is, bites it. Its venom is fast-acting, and as soon as the prey is largely immobile, the spider drags it back into its funnel to safely consume it out of sight. Many species’ funnel webs are horizontal, and found in grass and bushes, but others are vertical. Like most spiders, funnel weavers are nocturnal. Many species die in the fall, but a few live a year or two. If you find a funnel web inhabited, it is likely to be a female. Males spend most of their life wandering in search of a mate, and after finding one and mating a few times, often die.

Funnel weaving spiders are docile and non-aggressive, and their bite is rarely as bad as a bee sting. Funnel weaving spiders are sometimes referred to as “funnel web spiders.” True funnel web spiders are not found in North America, but in Australia, where their bite is considered harmful.

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Saddleback Caterpillars Preparing to Pupate

10-6-14 saddleback moth 006There is a group of moths (family Limacodidae) which are known as “slug caterpillar moths” due to the manner in which they travel during their larval stage, secreting a semi-fluid silk from their ventral pores as they move. These caterpillars come in all sizes and shapes. Among them is the Saddleback Caterpillar, which is much more colorful than the brown adult moth it eventually turns into. Saddleback Caterpillars are best known for their stinging (urticating) spines. Reputedly far worse than that of a bee, the sting of the Saddleback Caterpillar may be the most potent of any North American caterpillar. The larva’s bright colors serve to warn predators of its toxicity. Soon these caterpillars will be spinning cocoons (which can contain spines, as well) in which they will pupate until emerging as moths next spring. (Thanks to Rick Palumbo for photo op.)

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Grasshoppers Courting, Mating & Laying Eggs

8-20-14 mating grasshoppers 040It’s that time of year again, when grasshoppers are courting, mating and laying eggs that will overwinter and hatch next spring. In addition to adopting different poses and flashing brightly-colored wings, male grasshoppers attract females by producing calling songs. (Some females also produce sounds, but they are usually infrequent and very soft.) The males rub their hind femur against a forewing, or rub a forewing against a hind wing in order to make their calls, a process called stridulation. Tympana, or eardrum-like structures on their abdomen, allow both male and female grasshoppers to hear. Because the songs are species-specific, females can readily identify males of the same species.

After pairing up, the smaller male grasshopper usually mounts the female and the female curls her abdomen up to reach the male’s reproductive organ (aedeagus) from which she receives a package of sperm called a spermatophore. The mating process can take from 45 minutes to more than a day, depending on the species. The small, pointed structures that you see at the tip of the female’s abdomen are her ovipositors, with which she deposits her eggs in the ground.

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Second Brood of Woolly Bears Hatches

8-18-14  woolly bear 093Typically we start seeing Woolly Bear caterpillars in October, when they are searching for sheltered spots in which to spend the winter as larvae. With only two months between now and then, it came as a surprise when my great nephew and budding naturalist Eli Holland discovered a very young Woolly Bear recently. It turns out that in New England, there are two broods of Isabella Tiger Moths (whose larval stage is the Woolly Bear). The caterpillars that hibernated last winter emerged from hibernation this past spring, pupated, transformed into adult Isabella Tiger Moths, and proceeded to mate and lay eggs. It is these eggs that have recently hatched, and the Woolly Bear caterpillars that are no bigger than the length of your baby fingernail right now will be eating dandelions, grasses, nettle and meadowsweet nonstop for the next two months in order to survive the coming winter.

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