I sat in on a introductory entomology lecture about cockroaches this week, so this seemed like a good topic. Above you see my least favorite insect and also my frequent friend and visitor for night time assays in the greenhouse this past summer, the American cockroach.
I like this picture because it shows off a lot of great cockroach adaptations: the flattened body for fitting through tight spaces, the head tucked defensively under the pronotum, with the eyes wrapped around the top of the head for good vision in this postion, the long delicate antennae for sense perception in the dark, and the cursorial legs for running at high speeds.
My feelings about cockroaches have evolved since I entered entomology, and while I still don’t welcome them in my house, I now consider them fairly interesting to observe in other places and I even keep a small colony of hissers. I think I crossed a hurdle while I was desperately collecting insects for my class collection during my own introductory grad student course. After months I had somehow managed not to encounter a single cockroach of any species, which left me down an entire order. When I finally saw one of these large ladies scurrying across a pavilion floor I jumped on it with my bare hands. (In terms of weird cockroach collecting methods this still does not top the dinner doggy bag incident.)
A polyphaga cockroach, labeled with a photo of a darkling beetle.
I found these ‘Real Bugs’ lucite-encased specimens for sale a local grocery store. They’re pretty nice display items, and I’m actually kind of in love with the included collector’s cards which include trivia along the lines of “millipedes can have thousands of legs.” Above you can see the polyphaga cockroach, whose trading card inexplicably showcases a photo of a darkling beetle. Quick, someone calculate the taxonomy fail index.
I also love that they’ve not only hyped up the cards with “speed,” “size,” and “gross factor” ratings, but also “DEADLINESS.” This is kind of vaguely plausible for the centipede and “giant bee,” but what about the long-horned beetle? (Deadliness: THREE.) Frankly, I can’t wait to get my hands on the whole set.
A field roach in Argentina
A pretty little Argentinian field roach in the family Blattellidae. We have these guys in the US, too, but you won’t find them infesting your kitchen. These guys stay outside and feed mostly on flowers. Unlike many roaches, they are diurnal (active during the day), and frequent flowered fields and clearings. Roaches have always been the bug that freaks me the heck out, but apparently I’m fine with them so long as they stay out doors. Although there are over 4000 known species of roaches only 7 of them are considered severe pests. Most ‘wild’ roaches inhabit environments away from interactions with humans.
An easy way to distinguish roaches (order Blattodea) from other insects is the large, shield-like pronotum, which is often expanded to cover most of the head. The pronotum is the upper surface of the insect’s prothorax: in this case the large, yellow-bordered ‘plate’ just behind the head. This character is distinct even on wingless roaches, such as juveniles or the Madagascar hissing cockroach.
Science part’s done now. The roach-squeamish may be excused as I head into anecdote time.
Entomology is fun. As I experienced in Argentina, the reaction of a group of entomologists, on seeing cockroaches on the walls outside a restaurant, is to pause and discuss the species of the roach before heading on in to dinner. Most normal human beings consider this atypical behavior. Of course, there are levels of eccentricty, even within the field. For example, my labmate Paul and I took a break between courses to head back out and take photos. (These may show up here later. Are you excited?)
And then Paul (an avid collector) surpassed us all by sticking a few in a ziplock bag where they remained in his pocket during dinner. Appetizing!
Doggy bag of roaches!