By LESLIE BISHOP, guest columnist
Hot July days define summer for me. The heat brings on the first juicy homegrown tomatoes. The fish are hopping, and the cornstalks are getting high.
As a biologist, there is never a dull moment in July.
The dragonflies are frantically patrolling the pond, the cicadas are filling the air with the rise and fall of their chorus, and songbirds are busy feeding their hatchlings.
For many animal species, the warmth of July is ideal for reproduction and egg development.
Spiders are great examples; their eggs mature faster with warmer temperatures. This rapid development increases their chance to reproduce more than once before temperatures decline in the fall.
Wolf spiders, in the family Lycosidae, are one of my favorite groups of spiders because of their reproductive behaviors.
On hot summer days, I commonly see female wolf spiders in my garden with their egg sacs. After laying her eggs, a female wolf spider wraps the eggs in a silken sac and attaches it to her spinnerets (the structures that produce silk) on the end of her abdomen. She carries the egg sac in this way until time for the babies to hatch. She then tears the covering of the egg sac to release the spiderlings who clamber up her legs onto her back.
Each spiderling hangs on to a single knobbed seta (a specialized hair). Depending on the size of the adults in different species, there may be a hundred babies hanging onto the mom.
Wolf spiders do not build webs; instead, they are ground hunters. Using good vision and a keen sense of vibrations carried through the ground, wolf spiders capture insects by stalking and pouncing. The spiderlings must hang on tight while mom is on the hunt!
Some species of wolf spiders live in burrows lined with silk, and some of these burrows have silk and dirt turrets. These spiders hide in their burrows and pounce on passing insects.
Wolf spiders also are able to smell using scent sensitive hairs on their legs, and they can determine the palatability of an insect before they catch it.
Male wolf spiders find females by following silk strands on the ground that are scented with sex pheromones (specialized chemicals).
Many species of wolf spiders are active from dusk to dawn. Two of their eight eyes are specialized for low-light vision by having reflective surfaces.
There are few things more fun than going out on a warm summer night with a headlamp on my forehead to search for wolf spiders. Their eyes reflect a greenish glow, and if I carefully keep my light on the glow, I can approach the spider.
Sometimes when I am lucky, I will see not only the glow from the eyes of the wolf spider, but also hundreds of tiny glows from the eyes of the spiderlings on mom’s back.
Hot summer days bring cold lemonade, cookouts and picnics. But they also bring ample opportunities to observe and learn about the fascinating creatures around us.
Leslie Bishop is a Brown County resident and retired biology professor from Earlham College. She is a volunteer interpretive naturalist at Brown County State Park. She can be reached through the newspaper at [email protected].
